Which gaskets are you talking about exactly?
There's the foam gasket between the tail light and the car body, and then there's the gasket that holds the taillight lens to the body.
I bought a set of "Valenti" tail lights on ebay that had nasty foam gaskets, as well as one of the lenses being removed from the tail light.
I had to use a Dremel tool to chew all of the old black RTV sealant out of the groove of the body/housing.
I also needed new foam gaskets, but $35 for a set of replacements was offensive, to put it lightly.
I went to my local crafts store and got 9"x12" sheets of black foam for $0.99 each. Then I used my dremel to cut the outline of the gaskets. Link here:
https://www.michaels.com/creatology-...22%20x%2012%22
Took me like 15 minutes per gasket and $2 in material.
Very unfortunately, this is the only picture I took. Wow. RIP. But you can imagine.