Thank you for all the input. I have a big, 100 watt laser cutter so I don't really want to order laser cut letters from Gemini. I can't cut vinyl but mylar is OK. Vinyl makes hydrochloric acid when it's laser cut... not good for the machinery.
I must have seen the metallic acrylic in the Gemini catalog. Just wondered where I might get some. Brushed aluminum would be ideal for this job. I'm sure I've come across acrylic mirror somewhere too.
I will check the links in the thread. Thanks again.
Adrian