Infant bouncing solution for long-haul flight

My 8-month old is totally dependent on bouncing on our gym/yoga ball to get to sleep. We are trying to wean him off it and use other methods but still no results. He is a high needs baby so basically any change on him is veey difficult.

Next month I will be taking a flight with my baby, and I'm dreading not being able to have the ball for the duration.

Would anyone have any creative ideas about what could be used as a substitute gym ball during a flight? Ideally something like a sprung cushion we could put on the chair to mimic the ball's bounce.

Help please!