I got a custom pair molded at a gunshop in Chino. Although if you end up at the track, the org "TrackDaz" can now make some for you on the spot, I do believe
They make them out of medical grade silicone that cleans up super easy with soap and water, and it seems that they don't get that dirty that often anyways. I've been using the same pair pretty constantly for trackdays and any time I'm planning to go over 50 mph for over a year now, and they're still just as nice as when I got them. Although they offered free resealing if I need it down the line, so if they start to be less nice, then I'm still good.
I'm too lazy to keep buying disposable plugs, and my custom set stores easily, so I always have them on me and never have an excuse not to wear any. Best $55 in gear I've ever spent.