One online store here sold garters with the name and picture of T. sirtalis fitchi. The picture they used was of a wild specimen and I've seen it elsewhere on the internet as well as in at least one book (Rossman et al.?)

Most garters I've seen for sale have been correctly labeled, but not very accurately. Most of the time, they've gotten the species correct, but it's happened that they haven't been able to determine more than the genus. Apart from that first example, I haven't seen any store try to guess the subspecies.

Needless to say, there haven't been many opportunities to contact shops, because they haven't had any garters for sale. And I do hope none of my garters ever end up in a pet shop.