Flix, I know you're looking for some aftermarket stuff, not to make them. But since I don;t think there are any already made aftermarket scales for the RATs, I'm fixin to tell you what I did last weekend.
I put some 'squite scales on my RAT-3. I had a nice chunk of mesquite sitting around the shop. I took the Micarta scales off, made a pattern on some posterboard, and transferred that to the mesquite, which I had already planed down to about 1/4".
I carved them out, drilled and countersunk the holes, taped the tang, bolted them on, filed them down, sanded 'em out, put some shellac on there, and finished with wax. They came out pretty good and a guy at work wants me to make some for him. If I had a decent camera, I'd post a pic for you.