This is the bit I used. They have them up to 1/2" diameter :
BLACK+DECKER
1/8 in. x 2-1/4 in. Carbide Glass/Tile Drill Bit
$6.98 /each
This BLACK & DECKER 1/8 in. x 2-1/4 in. Glass/Tile Drill Bit is a specialty bit with a carbide tip. It is for drilling in tile, glass, ceramics and mirrors. It fits 3/8 in. drills or larger.