One thing I've done with smaller tanks is to make a wooden extension that sticks up from the top of the tank and has acrylic front doors. That way you can add light and have light plants, etc.
Either way, I love all the smaller Phelsuma and don't think you can go wrong with any of them. I don't know what species are available anymore. They do vary greatly in how easy they are to keep.
Another species that I really like is the long-tailed grass lizard. The scientific name skips my mind at the moment but I do think they are available right now. Faily easy to keep provided you feed them on the heavy side with faily small crickets.