I use Heat Bath Corp.
Small quantities?
It's been a while since I made a purchase. (maybe a year.) If I remember correctly, there was a 100-pound minimum (that's two 50-pound bags) of each material (Nu-Sal is for high-temp, Thermoquench for "low" temp). It sounds like a lot of material, but the stuff is pretty heavy.
I didn't think it was too expensive, don't remember exactly, I'm thinking it was something like $100 or $150 for everything, but I don't remember--I wasn't shocked by the price or anything.
It's good to have some extra lying around because it is a consumable. Drag-out alone adds up, then there's skimming, not to mention you've got to fill the tube to begin with, and the stuff kind of "cooks down" as is goes molten.
Try Heat Bath and get a quote. Good luck!