There are no lokka's for Landies (front or rear), so you're out of luck there.
I spoke to TJM yesterday about their pro lockers for a Disco, and yes, they have them on the market now, so I was informed. Around the $1250 mark supply only.
ARB's are a similar price to the TJM's when you buy in Australia.
I just purchased a Detroit Locker for the rear of mine, and an ARB for the front. Haven't got them installed yet, the ARB hasn't even landed. Detroit was $720 shipped to my door, ARB was $850 shipped to my door.
Search around the forum, you'll find loads of info to assist in your decisions.

