Baby food jars used to be the standard all-purpose hobbyist storage jar, but I don't think they make them like they used to, or if they're even jars any more. But, there are a lot of spices/condiments that come in smaller glass jars. For instance, I go through a certain amount of garlic paste, pimentos, capers, etc. which all come in small puck-sized jars with resealable lids that are perfect for leftover dye/stain, as there usually isn't much of it. That may be a bit pricey to buy and throw away the contents just for the jar, but that's where I'd go looking for them - the condiment aisle at the grocery. Find something inexpensive that comes in a glass jar, and there you are.