I’m going to suggest something totally crazy here. Especially since the OP hasn’t posted on this thread in a bit.
BUT, in the FJ Cruiser line the locker was built into every single vehicle, 2WD or 4WD alike...the difference was whether or not you had the button.
No, seriously, the hardware was there...the only option was if the button was installed, it was all a part of the wiring loom. Just had to buy a button and plug it in. Instant locker.
I’d suggest checking the 4Runner boards to see if the same situation exists here,
