Hmm... Would it be alright if Arty acquired the knowledge on how to build such a generator during his last foray into the multiverse, and then builds one here? It would explain how he made it home, and he did actually study one of them IC. Assuming that was what was on Clockwork Man's ship, at least. It would be a fairly large item, not usable in combat due to how cumbersome it would be to carry, so it wouldn't give him any immediate combat advantage, just access to his home dimension and supplies there.