A cat's a good idea. I got my first one, after I became disabled. Lots of lovely kitties waiting at the shelters.

One dog that still might work for you is a retired racing Greyhound.

Greyhounds are such VERY lazy, laid back creatures, that they are recommended for the disabled. They are 60 mile an hour couch potato love lumps. They are among the sweetest, gentlest, most affectionate breeds.

You also get a healthy, young adult dog that is spayed/neutered, and up to date on its shots, for a modest sum. Best of all, you're giving a home to an animal in need.
http://youtu.be/n7OYUgfEBa8