It's not about the helmets. Hell, we might have had 1000s of rocket launchers that we could have sent to the Ukraine.
The problem is with the heavy gear, like jets and tanks (heavy and light ones) and helicopters, ships. Quite a high fraction of them needs to be repaired.
Also procurement processes are quite complex, long, expensive and not very effective at the end.
For example, the German army is trying to buy a heavy transport helicopter, so basically either Sikorsky or Lockheed Martin. The last bidding processes ended after 7 years or so with no bidder being successful. (Both bids were deemed to be to expensive.) It's back to square one now.
Also, in the planning now is the succession for the Tornado and Eurofighter jets. Everything points to long bidding procesess, we might have a solution until 2030. And it will take a few more years until the new weapon systems are delivered - most probably some of them will have outdated gear by then (happens always with such long winded processes.)