There is no "reverse cluster" in a NP231 transfer case. While I will agree a chipped chain gear tooth or reverse transmission gear tooth is likely don't go looking or asking about a reverse gear cluster in a transfer case.
The D300 is a right hand drop case, TJ's have left hand drop F. axle. The adapter to flip and adapt a D300 to his AX15 is around $150 plus the cost of a D300, and the cost of an aftermarket shifter, and the cost of any driveshaft mods. Also it was mentioned to use a D300 with a 4:1 kit, this 4:1 kit costs around $700-800.
The Atlas, while a great transfercase the 4 speed version mentioned costs about $3000. So edco64 considering your TJ is stock and I will assume a DD either rebuild your 231 or buy a good used 231. The master rebuild kit runs about $200 which is about the going price for a good used NP231. While the above options are solution choices for your problem IMO they are just not worth the money in this case. The 231 is a good strong reliable transfercase, especially in a stock or mildly modded TJ. A few of us including myself are using the 231 with a SYE behind Cummins 4bt engines and in stock form this engine will make more torque than any stock big block. Next time you go puling stuff out of a ditch, use a winch.