Is it possible to buy just this gasket by itself? I see GM part #17110854 includes this gasket with the valve for about $40, but I don't need the whole thing. This is the washer/gasket I'm talking about. I need a new one because mine is seeping a little bit of fuel.

Google "Stat-o-Seal" or go here and search for "sealing washer".:

http://www.mcmaster.com/#

ACDelco 15-31054 or gm 52477087