Mirrors still make great reflectors. Especially if the glass is thin. You might have to glue the mirror to a 1/4" piece of plywood to keep it rigid and help prevent breakage, but it is doable. I would probably cut the mirror tiles into three pieces for a top and two sides. Play with the angle and the bulb placement until you see the most reflected light and you've got a pretty great setup.
used to carry specular aluminum, but I can't find it now.