Let's try posting this again - last time that silly forum error messed me all up.
I had another (probubly ill-concieved) idea for an idolo cage....
Why not a wooden bird cage?
The whole thing is MADE of sticks (rungs) after all, so gripping wouldn't be a problem. I think it would have to be wood, unless they have some other material that isn't too slippery.
Only problem would be humidity, but I will be keeping mine in a tropical plant grow chamber most likely, so I don't think that will present a problem. Besides, it will certainly be easy to mist them.