I have a local Schaeffer's distributor here that would most likely ship you any quantity of #131 you'd like. You wouldn't have to buy a whole case.
PM me for his contact info. I can't speak directly for him in regards to how much or how little he'd ship, and what it would cost, but I don't see why you couldn't work something out. I go there and buy #131 and my Schaeffer's oil by the bottle...Just as much as I need, when I need it.