All the usual supporters of our Turbo Regals should have them: Kirban, Jack Cotton, Poston, Bowling Green Customs, Kenne-Bell, and our [former] hosts of this board, Mike and Marianne from [formerly] Modern Musclecar (the new company name somehow escapes me).
If you are a little bit handy, have access to a few tools, you may consider cutting down the big diameter 160 thermos you can find for older cars. I actually did this with good results.