I got a ficus benjamina with the braided trunk and was able to pull the braids apart to create more vertical climbing branches and spread it out at the top. I thnk it turned out pretty good and is doing great 2 weeks later. Did not seem to harm the ficus at all. https://www.chameleonforums.com/spocks-cage-upgrade-56132/
I dont think it needs to be specifically a ficus benjamina or w/e, any species of ficus will work, if im not mistaken.
My GF and i recently bought an umbrella that was bonsai'd works perfectly with our little cham. We go ours from a local bonsai store, but this website http://www.bonsaiboy.com/catalog/under.html has some pretty reasonable deals on ficus' and umbrella plants.