Looks like Goodyear makes a small air bag that might work. The size is just about perfect to fit where the rubber puck is. Not bad fer $27 plus shipping.
1S3-013 Goodyear Air Spring
Actuation Force @100 PSI (Lbs.) Compressed 620
Actuation Force @ 100 PSI (Lbs.) Extended 140
A 2.40" (upper diameter)
B 3.40" (lower diameter)
I think the SumoSprings will be too stiff fer my application.
I could try a proof of concept fer the front dampener with some wood bracing and a tire tube or two.