@Colin (covering eBay part below) I'll give Suluk46 another look. I remember seeing them offering pre-sized windscreens but not materials or cones.
***doesn't look like they sell sheets/foil anymore. I'll shoot them an email later though.
This is the only one that might work for me. Everything else seems too thick or not wide enough (almost everything is under 4")
For the caldera cone shape, you need extra width to fit (I'll likely need somethign like 12x18") the cone pattern.
@Kevin, thanks for the site. I'll check it out when I have some time (got back from lunch and just wanted to check this quick before catching back up on work)