They are available from Lowrangeoffroad for about US$7.50 each or are piss easy to make yourself if you have a spare pair of backing plates laying around.
Just remove wheel bearings and existing backing plates, bore the centre hole in your backing plate out so the bearing will slip through it and then put back on axle tube.
Get the spare plates and cut the centre out of them, cut just outside the four bolt holes.
Then fit this to the axle and replace the bearing.
Refit axle to diff.
You can now remove an axle at anytime without having to undo brake lines or handbrake cables(if WT). A spare pair of axles is MUCH easier to carry in your car if they have this mod done.
Jas.