Attached is a fact sheet (from ACES) with a list of several apple cultivars recommended for Alabama.

You'll need to find varieties that not only have a fairly low chill requirement, but are still hardy enough to withstand late spring freezes. Don't forget to check into pollination (cross pollination) requirements.

Can't help you with where to procure your trees. It's been a long time since I bought any fruit trees. At that time, bare root stock was about the only option and a good one. They became available via mail order or local vendors in mid to late winter.

It would be a good idea to visit a local orchard or two this weekend, now that it's apple pickin' time. See what they're growing.

Here is a link that might be useful: Click here

I'm not aware of a good fruit nursery in AL - Classical Fruits, in Moulton was good, but I'm not sure they're still in business - but if they are, the Adairs did a good job and could certainly tell you which varieties were worth growing. There may be some AL nurseries - I just don't know of them.
Johnson Nursery in Ellijay, GA, Lawson's Nursery in Ball Ground, GA, Big Horse Creek Nursery in NC, and Vintage Virginia Apples will all have apple varieties that should perform well in most parts of AL. Just Fruits & Exotics in Crawfordville FL may have some selections that'll work for you in south AL. Stay away from TyTy like the plague; and I've been seeing troublesome reports about Willis.
Check the list from the Extension Service that rhizo(hey, cuz'n D!) listed above; but these nursery folks may also be able to recommend some not on the list - like MonArk, which is one of my top picks for a good early season apple(got mine from Classical Fruits, years ago).
Dr. Arlie Powell, one of the authors of the linked article, is now retired, and works with his son at Petals from the Past at Jemison AL - don't know if they handle fruit trees or not, but he might be able to direct you to an AL fruit nursery.

I bought some apple trees from Marvin's (home center) a couple of years ago, I have one 'Anna' and one 'Ein Shemer'(sp?). Neither of them have looked good since I planted them and I have no idea why.