we stopped carrying the puffers at my petsmart about a month ago ( i have the last 2 in my tank at home). I don't know if its nationwide but I know there isn't a store in the northern virginia district that carries them, so i'm assuming it is. maybe have to go online or see about ordering from a lfs.
and yeah, petsmart doesn't add any marine salt to their tanks, so i dunno if you confused about what store or something.
I found a semi local (45 min drive) pet shop that will order them for me when I am ready.
Of course they don't add marine salt, they only carry freshwater fish. I was there a couple of weeks ago and the employee that was helping me said that they use conditioning salt in all there tanks. He didn't tell me how much and how often though. I was just asking to make sure I didn't have to add the same salt to my tank... I see from the help that was givin that it is not needed.