Good morning!
We purchased a tool from our tile source (they have a website at modwalls.com but we visited their warehouse). They aren't listing the tool on their website but I think it was something like this:
Mosaic Glass Cutter
(ours are rather difficult to reach right now or I'd get you our model #).
These tools cut a slightly curved line but the curve is very slight. With practice, you can get the cut pretty much where you need it to go. Plan for some wastage. For safety, after lining up the cut, I would put my hand in a bag and squeeze, so any little bits would not fly through the air. I must say most of the time this precaution was unnecessary: I can't recall much chipping, if any, but it still seems wise
