Missing rubber seal for twist to close drain valve / any place to get just the rubber ring ?

[jazzisjazz]

Howdy all, Have a small problem with a leaking drain and hoping for a simple fix. I think the rubber ring is missing, I don't know if it would just be round or flat on the inside and angled on the outside of the same piece. Any help is appreciated. If I have the inside dia and the thickness, where should the outside be measured if needed to pick the most likely part to work and where should i look for it?

 

[Twowaxhack]

I believe that one just takes a thin oring.

Im Not sure what size, I have a big kit I try different ones. Take it to a good hardware store.

 

[Rickyman]

Bring it to Home Depot and see if it matches up with the universal one they carry