You can see from the studio locker room pic all gaskets were integrated...
Safe to say this is canon but they would have been fitted to the talent in advance prior to final build. The cloth gaskets sold now offer the flexibility to be tailored to the individual before fitting and, like you say, can also be removed and washed.
This is a new offering out of the U.K. by Fantasy Designs - a nicely integrated ribbed shirt. Cuts down strapping etc.