I bought about 20 gal and all the supplies to redo my decks, flybridge, entire bottom several coats/60z cloth and lot's more.
Have used plenty of West over the years working for various outfits...this stuff is very similar but lots cheaper..works the same in my book. They also have a volume discount matrix and offer great tech support over the phone.
US Composites
Fiberglass , Epoxy , Composites, Carbon Fiber - U.S. Composites, Inc.
But shipping is the killer so just a couple gallons may be cheaper locally.
FF is correct that most (probably all) of these retailers specify a formulation and the materials are actually made by just a few chem corps in the US.