Hello,
It's a tank bag. It's a backpack. The Firstgear Laguna GPS Tank Bag is best of both worlds. Even better, the Laguna GPS Tank Bag is a GPS navigation station that folds away when not in use. If you need to use just a map (or, if you're like me, you write your directions on a sheet of paper), the tank bag zippers off the base which uncovers a large, clear pocket. The Firstgear Laguna GPS Tank Bag expands vertically, while multiple pockets stow away all those smaller items you just can't leave behind.

Please Help.
Thanks !

I didn't find the right solution from the internet.
References:
-https://www.revzilla.com/motorcycle/firstgear-laguna-gps-tank-bag
-Support Platform video Examples