i have never seen one, its a conversion kit, but since dodge had its 400 convertable i think the public had no interest in a reliant convertable, why would you want to spend more money to make a convertable when you could have one right off the dealer lot.
It appears to be a kit. I think it would be fun to make one. It would be like having a custom car without the expense. Heck! Why not make a truck? Lincoln and Cadillac had no problem with it.