I have never used aero bars before either, but was interested in giving it a try for long-distance rides, same as you. After doing some research, I ended up getting these
Profile Design Supersonic Ergo 35c bars. They have a lot of adjustability and a bend that ultra-distance riders seem to prefer. I haven't even installed them yet, so I have no idea if I like them or not. Everything I have heard or read suggests that you won't like them if you can't get them adjusted for your fit preferences, and the less expensive ones don't seem to be as adjustable.