I too had a Skyport sunroof in my 78 elcamino, split windows! I miss it! Have you tried your local body shop? They have just about everything needed related to autos.
I typed up skyport in a search and found this web
www.crlaurence.com and click on automotive glass & acc, and it will take you to other links for parts, glass replacement, and identifying what windows you have to determine what seal you need! Hope this helps!! They also have a 1-800 #.