I also believed the sun rider is an LJ unique feature too.
Beside the after market tops that offer this option is a guy who design a kit to convert your regular top to a Flip your top. I quite expensive, I think he lower the price thought.
Other option is Stu Olson website. His friend Dave have a write up on what he does on his TJ, a good write up BTW, cool and cheaper that Fliping your top for sure.
I've seen the one on Stu Olsen's site and think it's the way to go if you want to convert a top - inexpensive and easy to do. One of the weak spots on the LJ is the plastic knuckle that allows the top rails to pivot. I don't think replacements are available and as shown, they're not even necessary. The nylon straps that were added are simple and a would snug things up. The LJ uses a spring loaded pin to lock the top rails when the roof is opened up. I've seen several that are broken or missing.