And even those could be just inflatable doughnut plugs with a pair of inwards opening flaps. You could even squeeze the air out of the lock, against the user's suit, to avoid the need for a vacuum pump!
also a 100% flawless vacuum wouldn't be that crutial, there's an atmosphere and you can pump more oxygen into the base, and also have maybe more "sphincters" to keep the air in.
https://en.wikipedia.org/wiki/Martian_lava_tube