I think the 1000 degree requirement is unusual, but probably not impossible, since the thermal shock testing would probably involve moving the test object from one -40 chamber into a second 1K chamber.
I used to work for these guys around 10-15 years ago: National Technical Systems (NTS). They are a testing company that tests (your) equipment. I don't know if that's a viable option for you.
http://www.ntscorp.com
Their web site is rather bland, but there is a section on thermal shock. They do a lot of testing to meet MIL Specs, or just customer requirements.
I was up in their facility in Boxboro, Massachusetts, mainly in "thermal vacuum" then. They are very accustomed to setting up one of a kind tests, and they have their own engineering dept. It was always in interactive process while i was there, often times the customer (you) could watch the testing and check in on your own equipment as the test progressed, or you can have them do things soup-to-nuts and send you a report.
Let me know how you make out, Jason
[EMAIL PROTECTED]
_____________________________________ Jason C. Dickinson Terahertz Scientist
Submillimeter-Wave Technology Laboratory University of Massachusetts Lowell Lowell, Massachusetts ______________________________________