Reddit mentions of Grommet For Bucket Lids

It's an S type airlock. You can find them at any homebrew store for less than a buck. I drilled a half inch hole in the center of the lid and attached a rubber grommet to create the seal.

It's a lot cheaper than buying the pre-made airlock lids.

These are the grommets and these are the lids, and it looks like you can just buy the whole thing already assembled.

I get fondant buckets from time to time, and I'll add the generic grommet and air lock to the lid. The best way to get the smell out is to scrub it good in hot soapy water, then rinse, then fill it with hot water and baking soda to absorb the remaining scent. It's usually not completely gone, but it's never been an issue for the things I've fermented.