Hello and welcome! My first question would be: Do you have a 3D printer? If you do stop by the Armory, I believe Jorge wears a Grenadier helmet if I'm not mistaken (someone who knows more than me correct me if I'm wrong). That one can be found here:
Halo: Reach - MJOLNIR Mark V - Grenadier. If you have a printer, the download is free, all you'd have to do is print it.
If you don't have a 3D printer, best advice would be to ask through here if anyone near you (or anyone willing to ship) would be willing to do a printed commission. I'd offer, but I don't have a printer.
I can't think of anyone who has made a mold/ cast of this helmet off the top of my head, but if someone has that may be the cheaper route to go with nicer results.
As for the fans, packages can be purchased from Etsy or even purchased in parts via Amazon or eBay (I went the parts and build it myself route as it was much cheaper). Best advice on fans, pack in 4 of them, 2 on the top of the helmet blowing the hot air out, and 2 on the sides providing a cross-wind to your visor so it doesn't fog up so you don't have to walk around semi-blind.
