But what vendors have in their inventory is (more or less) random no? They seem pretty rare to me. I've mostly seen Ethel selling them.
Ethel always has 3 of them on restock, also Aron can have 1 from time to time.
yep aron has them and speed potions as well and the wizzard in the toll house can have both as well .. i have a feeling i see them all the time so maybe others have them as well.