The three main companies are Blue Cross, RBC and Travelguard.
The first thing that all three will want you to be aware of is that medical insurance is for emergency use only. That means that if you think you're really sick by all means go and see the doctor and it will be covered one way or another. If you have a little tummy ache and want a prescription for an antacid, that's probably not going to be covered.
RBC and Travelguard are both very good with working with the hospitals. Both will pay the hospital directly. I've heard mixed things about Blue Cross, and I personally won't sell them.
You'll want to check what the policies on pre-existing conditions are, and make sure you mention anything like asthma etc. Anything, no matter how small it seems now, that might possibly become something complicated.
Oh, and CAA sells their own brand of insurance - since I don't work for CAA I've neither sold nor purchased it so I don't know what their rules, restrictions or regulations are.
Just an aside about insurance: I can't find my notes on it at the moment but a while ago I was at an RBC training seminar at they mentioned some case studies of people who did or did not have
travel insurance. One was a guy who was in florida and had a little too much to drink, attempted to walk out to the patio from his hotel room and didn't realize the glass door was closed. I believe that one did have insurance, it was covered, and it was a horrendous amount as well as a huge number of stitches.