I found the replacement gaskets here: Upgraded Gamma Seal Replacement O-Ring Gasket for 12" Lids Fits 3.5, 5, 6, & 7 Gallon Buckets (Pack of 2): Amazon.com: Industrial & Scientific
It appears I pasted the wrong link. Correct link is Upgraded Gamma Seal Replacement O-Ring Gasket for 12" Lids Fits 3.5, 5, 6, & 7 Gallon Buckets (Pack of 2): Amazon.com: Industrial & Scientific
Good price and fast shipping from here: Upgraded Gamma Seal Replacement O-Ring Gasket for 12" Lids (3.5, 5, 6, 7 Gallon Buckets) (Pack of 2): Amazon.com: Industrial & Scientific