Last year I made some light fixtures out of vintage glass insulators so I researched how to drill a hole in glass. There are numerous how to videos on YouTube. Here's how I did it and it worked perfectly. I bought a 1/2" diameter diamond hole saw at Home Depot. They are available in various diameters from many places but I wanted a quality one so I got a Milwaukee brand. (not cheap either). I used a drill press. I would NOT do it with a hand drill. I set up the insulator on the drill press on a wood platform clamped to the drill press with the correct size hole drilled in the wood platform to secure the bottom of the insulator. I used an old inner tube chunk with a hole cut in it that I was able to slip over the top of the insulator and seal around it to form sort of a mini pool. I filled it up with water over the top on the insulator forming kind of a mini pool about 1/2" deep. I set the drill press on the lowest speed then very gently nibbled my way through, ever so slightly at each plunge. Your lens shape would be difficult to secure but you may be able to rig up something to hold it steady and immerse it in something like a cake pan or meatloaf tin, whatever will allow enough depth to submerge it entirely at the drill point. Slow and easy worked for me. I suggest watching some YouTube videos and practicing on some jars or something first, as you don't get any do overs.
