I did some additional research and found an original factory installed Euro shade(p/n 51 46 1 944 199) that was NLA in the US. This is a longer shade that has hooks for the shade bar that are plastic and they mount into the headliner like the E-32's.

I purchased the Euro shade from European Parts Source (Non-dealer parts supplier) using the BMW part number. I cut the slot in the rear shelf and installed the roller blind. The headliner must be pulled down at the rear window to cut out the holes in the headliner for the plastic hooks. The installation requires the rear seat, c piller trim, door trim and over head handles to be removed, to pull the rear shelf and drop the headliner.

While this shade is much more difficult to install it is truly an awesome looking stock shade.
Total cost was $239.
If your M5 was built after 1/90, I would make sure your head liner has the cut-outs imbossed into the back side and that there are brackets welded to the roof to hold the plastic headliner mounted hooks. Unfortunatly you will need to drop the headliner to discover if the brackes are there. Maybe you can find someone that has installed this style shade in their late model E-34. I have had my M5 since 1991 and in all those years I have yet to see another E-34 with a shade!!!