if sulcata you can get them pretty much in every pet store but they are pricey there. if you really want one look on craigslist. lots of people selling baby ones for like $50-70 each. and if you want bigger ones like 20" + they are going for around $400+. was just on ca craigslist a few days ago. made me want to get a big one but nah.
just make sure you have a nice big enough backyard pref with grass. and gate/fence and make sure its goes below ground. cuz they are known to dig holes. dont need a huge backyard just enough.
but the aldabra's are a different story. they the 2nd largest tortoise get up to like 600lbs or something haha and those u need a huge yard. and they are expensive like 2k+ for a small one.