As amilla says, the best is OEM manual lockers.
You can find them in salvage yards on 4wd Trackers and Sidekicks
You can get them used from Hawks Strictly Suzuki (google them) and other vendors.
Since the snap ring is behind the locking hub, all you have to do is remove the six bolts that hold the hub assembly to the hub itself - not the ones on the end of the locking hub.
I hope that this helps!