While all JKs have a Dana 44 rear end, their innards are completely different from X and Sahara to Rubi!!!! You don't have the locker inside the rear end.. and the transfer case has nothing to do with the locker.
Why do you want a locker, what you plan to be doing with the Jeep will determine if you need a locker and what type. There are permanent lockers (wheels locked all the time, not for street use) air lockers, (like ARB locker, need a compressor to activate them, about $800 plus the compressor) Electrical lockers (like Eaton Elockers or ECTED about $700 to $900), manual lockers (like OX lockers, about $800) auto lockers/mechanical limited slip lockers (like PowerTrax No-slip or Detroit Tru-Trac $450 to $600)
And you need to know your gear ratio as it can be different parts for some ratios. Not sure if anyone makes a locker for the stock 3:21 ratio. I have 3:73 on my 08 X with the factory limited slip rear end.
08 JK Unlimited, soft top, 6 speed, 3.73 tow package, cruise, limited slip, 265/75-16s