I know what you mean about plugs,if you have them and still in
the service hang on to them.I was issued a gasmask without plugs
on an in the training with gas,I crawled through a wet spot to
avoid being shot and the alarm sounded,I donned my mask to only
blow out water find the canister plugged from water.Me dead

As for the elastic webbing,it looks like a simple replacement part.

The mask itself appears in good shape along with the cannister that
smells a little like cs gas.