[triactual]

UL94-V0 polycarbonate sheet or fish paper. Heatsink could easily get over the glass temp of common 3D printing materials like PLA or PETG.

[mewse-hn]

ABS would be fine, maybe printed in vase mode to be extra thin

[triactual]

Not flame proof though. You don’t want to put flammable things in something like a computer case that will be running unattended. I get that people do this stuff all the time with no issue. Just know the risks before taking them.