There should be clear map "pockets" available that mount with straps. Since the top shelter is plastic anything magnetic won't work... of course.
Some I've seen have a tab at the bottom to catch in the gas fill door and a strap to go around the triple tree to mount it.
I've checked a strap on today but could not find out how to install it properly. The only way I can think of is actually fasten the maps with tape, as TennesseeSmith suggested. I won't do that
I just contacted a dealer if he has a cable for my old Garmin Streetpilot 2610 to the accessory power outlet. And Bob helped me finding the correct RAM-Mount clamp. :ty: