Vinyl....
....Can handle the chlorine, if that's what you're afraid of. Wiping a gasket down with straight bleach, allowing to sit a bit, then rinsing with a wet sponge, usually kills the nasties. Then dry with a towel.
A little Armor-All rubbed onto the gasket after cleaning helps keep it supple.
If you have other concerns about chlorine bleach, such as one related to your own health, then perhaps other posters can suggest alternatives.