I got given a laser engraver. One of the cheap, no-safety-features-whatsoever ones from the usual source of such things. I've already managed to engrave the test pattern in the desk it was sitting on*. It is also extremely bright, even with the supplied protective goggles. 

So I am (quite sensibly if I do say so myself) currently building an enclosure for it. I'd like to include a window to keep an eye on things. Google has lead me to high optical density acrylic for this. However, I can't find an obvious supplier of this in NZ. Some overseas suppliers seem to suggest an orange tint, and the supplied protective googles are green. Any suggestions where I can find this?

The supplied laser specifications are 450nm wavelength and 7W power (this one).

The enclosure I am building is 450mm square, so the window can be that size or smaller. Depending on price, one easy option is to make the top 450mm square, but I can also inset something like a 300mm square window if that is a standard size.

* It was through the cardboard it was supposed to be engraving, so more powerful than I expected. And now I have a permanent reminder not to be stupid with it.