What's a reasonable price for fixing gorilla permits?

The question is easy - on top of the 500 US dollars which the permit costs, how much more should one pay to a tour operator for fixing a gorilla permit to Bwindi? I've already contacted the Uganda Wildlife Authority and they've informed me that for the dates I'm looking at they don't have any available permits.

So basically what's the going rate these days for this service?

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I have had quotes ranging between $0 to $100.

Some tour operators don't charge you anything extra if you opt to use another of their services, like transport to Bwindi. I believe $50 to $100 is pretty standard if you are only using the tour operator to get you permits, like hamidah indicates.

Thanks for the answers. For those interested I can now confirm that after having been in contact with a number of tour operators that the quoted price is somewhere between 50$ -100$.

If you car hire one of these company's cars to the park. They will not charge a service charge for fixing permits.