Try Bomar part number P100-51. The PO of our 1980 E38 used it to reseal the ports. As far as screens, are the frames still there? If they are, regular window screen material will work, using regular screen rubber tubing to hold it in place. Without frames will probably be much harder as I doubt the frames are available and Bomar ports which look very close still vary in size.
Don Wigle
Wiggle Room
E38 #8