try weathertech.com, they've got deflectors for any year xterra and they attach by using an adhesive, no drilling. i just got one for my '01 and it works and looks great.
I just ordered one from pinnaclenissan.com, and then went to my local dealer and had it installed. the installation was about 40.00 and the bug deflector was about 75.00.
Another vote for the Weathertech. On my 04 it attaches with 4 screws (into pre-drilled holes) and has two strips of adhesive tape for the corners. Very solid.
I'll have a pic of my nissan bug deflector soon, i'm waiting for my weathertech wind deflectors to come in so that I can put them one. The nissan one is pretty short, so short that I can't see the deflector when i am driving.