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2 things:
1) kathmandu is full of gear shops with plenty of good gear (and if you don't mind pirated gear, you can actually buy down vests/jackets/sleeping bags and fleece cheaper than you can anywhere else), so really since international shipping is expensive and risky, i'd plan on buying everything you can when you arrive in Nepal
2) you might not want to buy hiking boots locally since fit is so important when you are hiking for long distances... if you don't want your boots with you on your cycling leg, then you should ship those to kathmandu before you go. to do this, simply find a trekking agency that you'd like to use (if you want a guide/porter/cook), or even just make a reservation at a hotel and ask to ship a package to them for them to hold on to.
(newa chen in patan is a great hotel for kathmandu that likely can make reservations several months out. Hotel Tibet in kathmandu itself would also work.