The “TR-8R” thing was just a meme that took off. The actual character has another FN- number, according to one of the books. Anyway, where are you getting glass from? I’ve lost count of how many times I’ve seen the movie at this point, and that weapon has never once registered as being made of glass to me.

EDIT: http://starwars.wikia.com/wiki/Z6_riot_control_baton

It makes a certain amount of sense that the First Order would engineer weapons that could stand up to a lightsaber, what with Snoke’s and Kylo’s anxiety about Luke bringing back the Jedi.