Travelon Self Inflating Seat Cushion automatically inflates with a
simple twist and inflates without you having to take a breath of air!
Available at : https://www.corporatetravelsafety.com/catalog/self-inflating-seat-cushion.html
While designed for those who have to sit for long periods of time and want light-weight portability too Easy and compact to travel with, it stows neatly into its included carry pouch, so you can easily tuck it in your carry-on bag. Just twist the side vent and the seat cushion automatically inflates to desired firmness you choose. A little goes a long way, do not over inflate.
Travelers as well as non-travelers are using this self-inflation cushion because it is padded and ergonomically designed, not just a blow-up cushion.The self-inflating seat cushion is perfect for:
Long train rides
Long car rides
Long boat rides
Long bus or motor coach rides
Stadium seating and bleachers