As Gene indicated, aluminum, or even metal for that matter isn't a prerequisite for shroud material. PVC, wood (wood!?!?!), various plastics... sometimes what ever you can find laying around or cheap.
I like to go to my local hardware store (not a big box... a real hardware store) and just wander the isles. It's amazing what you see that triggers (no pun intended) a response in your brain for making a "widget", "thing-a-ma-bob" or "chingaso".
Of course the flip side of that is you buy a bunch of "hardware" to make your masterpiece, and before you know it you have more invested in your DIY bit than had you just bought one ready to go. I'd bet a price quote from Gene would have you re-considering... unless your like me and you write off the cost as a "learning experiance".
Have fun with it,
C