It would be nice if clients would bring whatever brand of condom they are comfortable with and know fits snugly, but that is impractical.  I admit to being a newbie (pending approval with TER), but I feel that with the world being what it is, best for the provider to take brand requests if need be, have several sizes/types available, and trust ONLY condoms she personally buys and inspects.  Probably (hopefully) some urban legend, but I heard about a vengeful, evil whacko who purposely put tiny pinholes in his condoms to pass on the HIV he got from an unknown woman.  Why take a chance with what could amount to your life, ladies?

Providers have always come prepared for the party in my experience with common brands of condoms, but I do need the snugger kind or they will easily slip off due to my shape. Slip off during a good grinding CG is a big worry and distraction for me.  

So recently I have brought along a favorite brand with a good track record and hope that the provider will accept them at that point or that I can work out a way of asking for them on the next visit.  It only takes one near slip off to get the point across.

I also bring a favorite lube - it is interesting how just the lube can be the point of serious discussion as to which brand is better.