They gladly sent you the MSDS, to keep you safe. But they didn't give you enough information to replicate their product. That was obviously going to be the case, and I don't see how you expected anything different. However, let's try to work with what we have:
They list a bunch of solvents, and their percentages. They don't mind doing this, because its hardly a trade secret. In fact, even though you've been told -- MEK (Methyl Ethyl Ketone) 55%, its now up to you to get it right: 55%, not 54%, or 55.67%, accurately, all the time. So they're not afraid of you putting them out of business. Even if it doesn't really matter for functionality, you can't claim the same quality that they claim, so you can't sell it. I'm just putting things in perspective here -- what's possible and why.
The glue itself is some sort of plastic, made of two types of resin, and a co-polymer. Those are trade secrets. No one will share that information with you. Once they had it, they'd make it and start charging you for it.
We can only guess what this plastic is. The solvents dissolve the resins, and soften the foam, and the plastic of the mask, without ruining them. (or at least, ruining them only slightly, given this is a part that doesn't show.) After the solvent evaporates, the co-polymer and plastic form a continuous plastic with the mask and foam.
Its not very likely you'll be able to find this at the local hardware store, but you probably don't expect it to be that easy.. However, if you know exactly what plastic the foam is made of, and what plastic the mask is made of, we might be able to find out what plastic they have in common, and maybe find a distributor who'll sell you some.
I don't want to completely discourage you, since you have a pretty clear application, and I can see how moderate cash outlay could work to your benefit. But this has the potential of rapidly becoming a snipe hunt.