Salwar kameez

Not all salwar kameez are sleeveless; indeed most definitely have sleeves. They can have all types of sleeve, too - long, short or elbow length.
But why bother? You don't need to wear salwar kameez to be modestly dressed in India. In fact you'd be more comfortable if you didn't as they don't have pockets and the shawl (dupatta) is a real nuisance - it's hot, it falls off and it gets in the way of your day pack. If you do want to wear salwar, you can buy them easily when you arrive.
Classically cut, conservative western-style clothes are quite all right and more practical. Just don't wear anything clinging or revealing: no cleavage, no expanses of flesh, no tight-fitting T-shirts. Imagine you're a missionary on holiday and dress accordingly.
Another alternative is a long-line traditional Indian top (a kurta) worn over a skirt or your own pants. If the top is see-through, wear a lightweight camisole underneath. These items can easily be bought on arrival as long as you are not a big size. If so, you'd better bring your own things.

If you are worried about harassment, note a couple of things: (1) the way you behave is as important as the way you dress; e.g. avoid eye contact with men who stare at you; be wary of conversations with strangers, and so on; and (2) most men who hassle you will be touts who are after your money, not your body.

Cool, I'm not into tight or revealing either. The kurtas look good, quite comfortable.

the consensus i've gotten is that you don't HAVE to wear Salwar Kameez. you might like to, however. i've worn them before and find them very comforable and convenient. not to mention that a lot of my own western clothes don't have pockets, and the dupatta doesn't really get in my way. but they're certainly not mandatory and dressing "modestly" will probably be fine. you can always pick up a few if you feel like your own clothes aren't sufficient.

to answer your original question, if the websites seem to cater to the US (i.e. a US domain, prices listed in $ instead of rupees, shipping domestically, etc.), they probably are more for the American South Asian market, including american-born young women with american sensibilities, for everyday wear in the US, where, obviously, they are used to wearing sleeveless tops and more revealing styles even though they are ethnically Indian.

for another thing, Indian women can get away with wearing slightly more revealing clothing than western women can, because they will blend in better in general, not to mention they know the deal and where that is appropriate and where it isn't. Indian women know how to pull off a sleeveless top without being overly revealing. also, you can apparently get away with tops that are overall "modest", but don't have sleeves. there's a big difference between the sleeveless SK i've seen and the tank tops most american women wear.

oh, and keep in mind that the american concept of "tight and revealing" is a tad more forgiving than the south asian concept of same. for instance a knee-length skirt in the US is considered downright chaste, whereas in india it might reveal more than you'd want. in the US "tight" is spandex. whereas from what i understand in at least some parts of india "tight" is like "visible evidence that you have curves".

Sleeves are better always. Just that you get that funny tan after walking around in the sun in short sleeves.

Me personally, i wouldn't bother with sleeves except if i was going to be in the north in winter. I don't care if indian women can get away with more revealing clothes, Sleeves are hot. And i would resent the fact that indian women aren't expected to wear sleeves while we are (which i don't think is the case actually). Yes, i know its about avoiding harrassment in which case, i would say, cgame's advice is intelligent.

Have you considered getting your SK in india when you arrive and flesh the whole problem out for yourself once there. Less chance of making a mistake. And it will be less expensive also.

Legs and 'frontage' are the things to cover up and you can do this with loose cool western clothing or salwar kameez. If you wear a skirt have it at least to calf length. In the cities a popular choice with young Indian women is jeans and a kurta top - I think jeans are awfully hot in the hot time, so a loose top with loose cotton pants more cool. if you are trvelling in the winter jeans o.k. In the heat, salwar kameez with the drawstring around the waist is cooler than tight belts or elastic. You need not necessarily wear the dupatta (long scarf) - I have seen many young foreign women with salwar kameez and no scarf (which can make you hot) and they look nicely appropriate in Indian culture.

ah, well, how many times have i heard it said that it is "incorrect" to not wear the dupatta. You look "undressed" in indian eyes if you are not wearing it, so no doubt all those foreign women not wearing the dupatta are making yet another faux pas.

You can just drape the scarf so loose that it barely registers with extra warmth.

Salwaar Kameez are very comfortable as they're loose and airy and so easy to put on in the morning. The dupatta gets some getting used to and after a while it doesn't get in the way anymore. Whatever you wear, just follow the guidelines above and you'll be fine. A lot of Indian women in the cities love to wear Western clothes so anything goes as long as it's modest. In more rural areas or when travelling on trains or buses, still to SK with dupatta. Buy your clothes in India - they're super cheap. A good place to start is Fabindia (a bit more pricey but the selection is great). Look at their website to find out shop locations.