You could use a piece of epdm rubber riveted to a spring loaded hinge, problem is it would take a bit of trial and error to get the spring tension right.........

Pr you could use a 8" round barametric damper and adjust the counter weight to open/close correctly.........

or just run by dollar general grab a small stainless steel trash can, the kind with the foot switch.......step on switch open lid, then when things slow down transfer to big cooler........