I have a nearly new CoverCraft car cover (WeatherShield). It is custom fitted for the M5 but will fit any E39 5 Series.
Link to Covercraft
It does an excellent job of keeping SUN, BIRDS & TREES off of your E 39. It is gray in color,very lightweight and stores easily. It takes approx 2 mins to install and 2 mins to take off. The only time it gets tricky is on a windy day. The material feels like a parachute.
If you keep your Beast reasonably clean (as I'm sure most here do) the cover will not scratch your finish. I used mine on a LeMans Blue and experienced absolutely no issues.
I also have the locking cable (unused).
The cover is machine washable and fits in the dryer too.
Let your friends and co-workers refer to you as a car geek as their cars stain and fade into the sunset.
I paid $260 for the cover in June.
My slightly used price is $125 plus shipping.
Regards,
Al