So, wanting a couple of mirrors to buonce my 532nm thing around on I found a UK company called Scientific Mirrrors .. two 3mm thick, 2" square surface silvered mirrors for £10, delivered.
Bargain. They do any size, on any thickness of glass, quality is excellent, edges nicely ground etc. Just passing it on, I have no commercial interest in the company and they didn't pay me to say this![]()