I printed out a few fan shrouds and they either cracked, melted or both. The original shroud is made out of metal (stainless), but I made mine out of copper because it was easy to bend. You can also use aluminum or mild steel. I'd avoid galvanized because it can emit toxins when heated to high temps.
I am working on flattening the UM2+ shroud. I'll try to post that up when I am done...A new one is $40+shipping.