Is there a power drill bit available to pierce glass?

You can drill the holes with a Dremel tool and a diamond bit. You can create a little reservoir with plumber's putty around the area you want the hole. Then fill the reservoir with water. 1/4" deep would be fine. You just want to keep the bit wet so the glass doesn't get hot and crack.

Rather than possibly mess up a nice ornamental glass maybe you could consider getting someone

at an art store that teaches stained glass techniques to drill it for you. After all, how often are you

going to drill ornamental glass??

You might look at a small Dremel hand drill (mostly for craft projects) and see if they have tips that will allow the drilling without shattering or crazing the glass. I bought my little Dremel at Home Depot about 2 years ago and don't use it enough but that's because I'm not as involved in "crafts" as I thought I was going to be when I bought it.

Good luck!

Check into a glass drill bit. Doesn't matter what drill you use you need the right bit otherwise you will never get a hole in it.