Most fuel caps are simple to engrave, I can just about put what you want on them. The layout you see in the pictures are the norm.  They are $24.00 for the set plus the shipping based on the rate to your area.

     
Engraving process starts by layout in CAD      Then they are put into a custom fixture

     
I then apply a cutting oil for aluminum         they are engraved .030 deep

The finished product!! It's shown in black and white so you can see the engraving
a little better