AIRSHIP RENAISSANCE can’t deal with helium shortage. “The military is so eager to get more airships in the air in places like Afghanistan that industry cannot keep up with its demand for helium gas and helium gas containers.”
So fuel the unmanned ones with hydrogen. It’s not that dangerous, and it’s not like you’re putting humans at risk. Sure, it has a tendency to migrate right through containers, but they could handle that in the 1930s, so we can probably handle it now.