We know that here in the u.s. you can't get a jumpseat ride.....SO, what would happen if, before the flight, you asked to speak with the Captain and you say something like "I'd really love to take some flight deck photos in flight but I know we're not allowed up here.... if I give you my camera for the whole flight would you be able to take some photos like maybe some scenic photos out the window and maybe some showing the instruments etc?"
And you'd have a small camera, loaded with film of your choice, ready to go, and let them have it until you disembark at the end of the flight.
do you think they'd do it? You could even tell them you'd email them some photos for themselves or mail some prints to their address at the airline. I've seen quite a few photos on here taken by crews while inflight.