Smacks wrote:The helmet is reminiscent of a German stahlhelm, which was somewhat derived for the medieval sallet.
For futuristic helmets of that type, I'd also lean towards Eisenkern or Dust Tactics. For medieval helmets, I think Perry Miniatures has quite a good range, which includes sallets (not sure about scale).
I also found these, which are fantasy goblin sallets:
According to
this topic they make decent human helmets.
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Anvil industries also has this sallet "type" helmet with a face mask:
http://anvilindustry.co.uk/Infantry-Heads-Helmets/regiments-medieval-helmet

Definitely think you are right about the later medieval/German style with the armour. In fact, looking at this I would say the props for the film probably came from that - mix of a medieval armour plate and the top of a Japanese Ashi-Garu or Samurai helm.
For the medieval perhaps try the Perry War of the Roses or Hundred year war plastic men-at-arms kit. I'm not sure where you could get the upper element of a Japanese medieval helmet from - Warlord Games now carry a plastic kit but think the heads are moulded with the helmets which would make conversion a pain. You might be better off with one of the specific casts shown above, although I would be cautious of proportion as the Perry plastic men-at-arms are realistically (rather than heroically) proportioned, and you don't want pumpkin heads