I remember having this discussion with someone before and I certainly wouldn't trust cheap safety glasses to protect my eyes. The one I use at work cost around £350 I think and will protect my eyesight from a direct strike from the laser, which is 3KW co2.
The question is "How much is your eyesight worth?" I would look in to getting the correct glasses for your machine while you still can.
Anyway Planetside2 is calling. "Live free in the NC"