Russ,
This looks like the people that produced the endcaps for Gulf Stream:
http://www.globalmoldingtech.com/global.html
Here are their point of contacts:
http://www.globalmoldingtech.com/contacts.html
They were or are also known as "Global Glass Inc" & they are located in Elkhart, IN.
I doubt very much they will be able to help you though. Generally, a company such as this is not allowed to produce end caps off fixtures because they are owned by the customer (Gulf Stream). Won't hurt to try however. Good Luck getting any cooperation from Gulf Stream. It would be nice to be pleasantly surprised. Let us know what you find out.