Since the site won't let me direct link and doesn't show a part number SO... go here: http://www.mopar-parts-dealer.com/parts.htm
-Enter year/type of Jeep
-Go to: Front Suspension > Front Axle and Carrier > Axle Assy.
I think it's called "Nut Back" and is $11.40
Double check though. Click on the illustration to be sure.
Also, I know it's not going to be an OEM part but if you can figure out the size/thread I'm sure you could probably find it at Mcmaster too. www.mcmaster.com
They have everything..
Hope this helps