That is a plastic sight glass (polycarbonate). It might fit, might not. Even if it does, a bigger concern is it melting mid-brew from the heat, unless you use a heat deflector- see BobbyM for videos.
You should be able to find the proper diameter/thickness glass tube at a lab equipment supply house (several in Austin), or maybe a specialty glass shop catering to artistes. It is just standard borosilicate tubing (pyrex, kimax, etc.)
It is probably too late get a glass one if you need it for a brew this weekend. Had you contacted me yesterday, I could have located one. I don't know why you bother asking on HBT, when you are well aware that I am all knowing.
If you are going to try the AHB one, it might be a good idea take your sight glass holder with you, or your whole pot, to make sure it fits.