These are for the Pathfinder but they fit the Xterra.

Leather Shift Knob: 32865-40U10
Leather 4x4 Knob: 33218-32J08

Obtained from Pnutmnm on XOC. Leather Shift Knobs on XOC (http://www.xterraownersclub.com/ubb/Forum4/HTML/000597.html)

I think there is a mistake in the 4x4 part number, I just bought one and the part number is 33218-32J03

Richard