Thanks guys.
I appreciate you all's inputs. I used the template-and-cut-to-shape acrylic mirror method before posting, but thought there might be other "professional" (i.e. purchased) ways of doing this.
I used the cheap Wal-Mart cut-to-shape CIPA Replacement Mirror (
http://www.walmart.com/ip/CIPA-Cut-a...irror/22614764), and really liked my results for a $7 piece of shiny plastic. Had to think about some considerations like strength, heat dissipation, ease of handling, and aesthetics, in that order, but so far it seems it will do the trick.
We'll see how they withstand the heat after several hours of operation (although I'm using AeroLEDs which are, theoretically, cooler).
Thanks again.