If you don't want to buy the bit/kit from GlassHoles.com, like me, you might consider an LFS:
I was told by the woman at Elite Reef, they can drill tanks. And I know (Sai?) the owner of Exotic Aquatics in Boulder can drill. I forgot which store told me about $25 a hole, you supply the bulkhead/fittings. I didn't inquire what their "guarantee" is if they crack the tank though, you might be S.O.L. I know Sai's probably done it a thousand times, so I'd trust him. Been buying fish from him since I was like 12 yrs old in the 80's, lol.