Most chain stores do not carry them - your best bet is to call around the mom n pop stores. Most often, you have to order them. It's best to find reliable breeders on forums - the two most popular sites out there where you can buy them often have poor stock and very bad advice....for instance they will tell you that it is acceptable to keep 2-3 adult axolotls in a 10 gallon when really the 10 gallon is barely acceptable for one adult.
They also require a bit of care...for instance their water needs to be temperature controlled - it needs to stay cool (under 70*F) year round, no exceptions. Even short durations of 75*F can stress them to the point of death very quickly. That is a huge thing to take into consideration for the those who might want to keep them.
No, he spits it out before he swallows any food It's really the only substrate they can be on since if they have gravel or any rocks smaller than their mouths, they just swallow it and it gets impacted in their gut. They used to have a 3D foam background that had a floor to it. That's ideal for them really, but it's so expensive!