There are several shops in our area called 'Tap Plastics' that specialize in all kinds of plastics...They have acrylic sheets that area 'mirrored' on the back just like glass mirrors, but MUCH lighter! They will cut to any size you want...
Here's their web site:
Clear Acrylic Sheets - Mirrored: TAP Plastics
Look in your local yellow pages to see if you have any Plastics type specialists in your area that might handle a similar product...
I replaced two of our mirrors in the AS with this product, and couldn't be happier! I was able to 'glue' one mirror to the back of a wardrobe door, then added some edge clips for added security - worked great, and didn't add any appreciable 'load' or weight to the hinges...