I'm looking for a good sporting goods store to buy an authentic (not knock-off) large backpack. I've found the North Face store in Siam Discovery Center, but don't really want a north face. As well, I see all the stores in Khaosan, etc., but they all are knock-offs and I need something that will last.

Can someone recommend another store? I'm thinking something like a Trail Outfitters or REI store in the U.S. Any help would be greatly appreciated.