Would be easy to simply have the speaker holes pre-cut. Almost any glass shop takes custom tempered glass orders. All you need is a good diagram and you can have your glass a week later.

I've got a toothbrush from these guys and echo the comments that it's functionally deficient. The head is too small, the forward bend of the handle awkward , and the neck itself is far too flexible. On the other hand, I love the mission. I hope these guys iron out the kinks.