Most arboreals aren't snakes that do well being handled, or at least not the ones I've dealt with. You could start with a carpet python though, they're semi-arboreal and just great snakes, and can be handled regularly. There's a good caresheet on this site for them, or google them and there's lots of info out there.
If you want to check out some other species though, look at Emerald Tree boas, amazon tree boas, green tree pythons