maybe a piece of 1/16th sheet metal, thats rust treated and you could use a chrome spray once its fabricated. Just put a break in it where you need the bends, (I dunno if you have access to a hand bending break). Otherwise here is a site with directions on making a quick and easy DIY Break.
Get yourself some reflective Mylar. It's basically the same stuff as the inside of those Helium party balloons. Here in the UK you can buy small quantities on eBay, but in the US it only seems to be on large rolls - perhaps you could find just a small bit if you do some searching.
I would say get some large diameter pipe, cut it in half and line it with Mylar. Cheap and very effective. Mylar is used in hydroponics and other high light intensity plant growing activities (not always legal in all countries )