OK, how about one out of a 1,000W MH? The material is what you are after as I'm assuming you are going to fabricate something.Sure, but the orientation of the bulb changes, and renders it useless.
In this fixture, the HPS bulb is mounted horizontally, and tucked inside the reflector inside the top of the fixture.
This has to be removed, and a new one made.
add: If you want something new, buy some fixture insert material, like this: