couldn't you just make your own gpo insert's out of a spare set ? buy maybe doing something like this :
1. First cut out the mesh from the grill insert (try to ge as close to the edge as possible)
2. use a dremel with a sand wheel using xxxx grit sand paper
3. After you have a the nubs sanded down and level with the rest sand down the rest of the insert using xxxx grit sand paper to prep for painting.
4. Paint the inserts the color that you want and then re-install
rough draft not to much detail (just a thought maybe it would work maybe not if i had an extra pair around i would sure try it just to see)