Horacio said:
i]Hey, man, when are you going to have product x?[/i] (for example Dragonstar)
-Product x? What is that?
-A wonderful new d20 product!
-I've never heard of it, it must have been cancelled. Why don't you buy the new Warhammer book?
-Funny that, I have a copy right here I got off the Internet
Trust me, don't support those who won't support you. Does the Brest guy have gaming tables? If so, then start up d20 RPG games (I assume you mean he pitches Warhammer wargames. If he's pitching the old WH Fantasy RPG, it is getting support now. Comprise and run a WH RPG for a while, then switch down the line.)
Try running a d20 WH Fantasy game if he's not a big RPG fan. The Scarred Lands setting pretty much has everything you need some of it is the right flavor too.
When others start asking for the product, he'll either get the clue or they can order off the 'Net. If he starts getting nasty and theatens to kick you out, tell him to start selling the products you want or just try to special order it for customers. If he does kick you out anyway, I think you will find other d20 players eventualy and they won't be at that store.