Larry, Try MSC Direct: www.mscdirect.com.
Go there, type heat shrink in the quick search box at the top of the
page and click the Go button. I don’t know if it’s glossy, but a quick
search on my part shows that you can get at least some of it in 48"
I’d also try www.mcmaster.com.
My experience with these two industrial suppliers has been excellent.
If you can’t find what you’re looking for, you can send mail and
they’ll do the search for you and get back to you very quickly.
Christine in Littleton, Massachusetts, USA, where most people are
wondering what happened to summer but I’m enjoying the return