Where can i get ribbed aluminium or steel sheet?

[Thenewguy]

I don't know if this helps try onlinemetals.com

[WhiteWolf McBride]

Hmmm, another idea.

Try the mirror-coating for automobile glass. You may not need the ability to see thru it from the backside, but the reflective aspect to prevent others looking in might be what you could use.

I'm sure you could scavenge a scrap from a tinting shop to test it out, and if it works, buy a bigger section.

WhiteWolf