Gasket for big mouth bubbler?

I just received by first plastic big mouth bubbler. Seems pretty cool, but I have seen lots of comments about difficulties in getting a tight seal of the lid. I can't believe the plastic one doesn't come with a gasket for the lid. Has anyone found a decent gasket which will help better seal up the lid?

I bought the gaskets for the glass ones and cut them down to size for my lid. Works great. Cheap and easy

I haven't had need for a gasket on my 3 plastic ones. Just cinch down the lid a little tight and it works fine - I can hold the whole thing upside-down with a couple gallons of sanitizer in it without leaks.

I have two that seem okay, and I check them during use to make sure they remain tight. I'm thinking some may have flashing that is not allowing a good seat.

I've used 3 layers of sanitized saran wrap. After sanitizing, I lay them flat over the opening, put the white lid on, then pull up the layers hanging outside the white lide so they are not in the way of screwing down the blue lid. Once I screw on the blue lid pretty tight, I use a sanitized knife to cut a hole in the saran wrap where the airlock hole is. This seems to work OK. I'd like a nicer permanent gasket but this has worked for me so far.