This is the only reference picture I could find:
But I've read MeruPuri and love it, soooo..... <3
Well, I think you're going to have to break out the power tools (and the measuring tools, at that). It looks to me like you could just cut the mirror into a heptagon (or buy one, I think they might sell them like that) and use strips of wood to create the sides, and then paint them. I don't think the strips actually overlap (I don't remember if they do or not, but I'm guessing no) so you would have to plan it so that they'd join together properly. Then when they're all made to fit together, you could cut a slot on the inside of the frame for the mirror to fit in, and then glue it all together with a strong glue.
The real problem with the mirror would be the measuring - everything would have to fit together perfectly or it wouldn't work. You could always draw it at 1:1 size on a piece of paper and just cut out the wood according to that pattern.
That's just my two bits. I think wood is the only cheap, viable material for making such a small object. You could always make a model and resin-cast it, but to tell the truth you can probably get pretty nice results from just painting wood. In my opinion. >.> Plus, strips of wood are available at any Home Depot, and small mirrors are available at a lot of places.