You can do it yourself if you have a Dremel...go to your favorite hardward outlet, and buy a tile bit. Take your bulkhead and a marker and draw a circle where you want the hole. Take your Dremel and score around the drawn line. Now spraying water, (careful the Dremel is ran with electric current), work the bit back and forth about a 1/4 of a inch, until you have a hole through the glass. From the hole continue around the rest of the circle.
Dan drilled 4 holes in my 180 using this method.
The water cools the bit.