I use wooden plaforms for my Robo, but I have covered them in
plastikote , which so far has been great at keeping pee at bay, and makes the surfaces quite easy to clean.
I made one of the platforms myself out of popsicle sticks, and the other one I use is from
Getzoo. Getzoo also sell
a ramp to go with their platforms, but I've just been using straight bendy bridges, which work like a charm.
(I recommend using Chrome with a Google Translate extension for the Getzoo links.)
Hope this helps!