If you are looking for a clown that will surely host, go with a clark's clown (4"). In the wild, they will host all 10 natural clownfish-hosting anemones. In captivity they will host condys (which are a bit easier to keep than clownfish hosting anemones), toadstool leathers, hairy mushrooms, etc.
If you're looking for something small, go with percs (2.5"). However, percs are a little more picky when it comes to anemones. In the wild, they will only host the ritteri anemone (h. magnifica), sebae anemone (h. crispa), gigantic sea anemone (s. gigantea), and haddon's anemone (s. haddoni). These natural hosts have a record of being very difficult to keep. However, in captivity mine have gladly accepted a BTA, which is considered by many to be the easiest clownfish-hosting anemone to keep.
A lot of people will tell you that
TR percs will not host anemones. This is not true. I have kept
TR clowns for a few years now and have experimented with different anemone and surrogate anemone relationships. From my experience a pair of
TR percs will glady host. If kept singly, they are less likely to host. Hope this helps.