Rover Accessories had them last I checked. Though you'll find reports on customer service to be hit or miss, though I have never had any problems. I think they are on par with Eezi Awn and perhaps better than ARB?
I bought mine years ago in disrepair and replaced the floor and reconditioned the canvas, screen and some ther things. We (wife and I) used the heck out of it and I recently sold it because I have a little one and a 60lb. pooch that will likely need more space. So in the mean time I will be ground tent camping until I can afford another larger RTT to hopefull go on a trailer.