I don't have a GPS for you, but I do have a mount for it that I used to use on my 2610.
I don't use the mount anymore since my GPS is now mounted on my tank bag, real convenient since I ride 2 bikes and switch the bag back and forth.
I believe the body styles of the 2820 and 2610 units are identical, and the mount would work.
It has a RAM ball on the back of it.
Also have a RAM ball mount for 7/8" bars and Ram arm (4"?) with spin lock available.
Lemme know if you think any of these parts might be useful for you.