marker light hole on after market quarters

X2 on the sanding/filing after paint. most of the time you have to do this for all the holes.
Use a fine half round or rat tail file and tape off around the hole to help eliminate scratching if you slip.

If it's way to small you can use a uni-bit/step drill. Just tape the area with masking tape to eliminate the possibility of chipping. Touch up the exposed metal with paint once you get it to fit then install the signal light when dry.

Good luck.

Pic of Uni-bit for reference...

http://www.staples.com/office/suppl...&AID=10422268&partNumber=763346&storeId=10001