From the 787 pilots I have discussed this with, they don't know of a good workaround for GPS in the back of the bus for the reasons noted by our friend StuckInYYZ . I've heard a variety of stories from mounting the external GPS to the furthest back window on the captains side, to an interesting tape effort to the escape hatch are successful; but alas I'm not sure those will help those of us in the cheap seats too much.

I'd find a friend with a suction cup mounted GPS to try in a 787 before you spend money on one. Hopefully 2021 will yield some long-haul flights for me again; if so I'll try it with my Stratus & Foreflight. I don't normally carry that for commercial flights, but I'm all for experimenting. #science