You are going to pay big bucks no matter what you do, unless you go the junk yard route. The best t-case would be an Atlas2, it bolts right up with only a 1 inch spacer on the tranny side if you have an AW4. The only problem is you then need 2 new driveshafts and you have to cut up your floor a bit.
Do you really need more case than what a NP231 can offer? Do you want lower t-case gears? The NP231 is a good case and you can buy them over the counter with lots of options(4:1, SYE, HD Chain). They bolt right in and your front shaft will fit. Or you could get a case from a TJ Rubicon, but why spend that much, when you could just get an Atlas..
Greg