As mentioned, I made the decision to go ahead and construct the cowl out of card pep / resin, for a number of reasons which include the following three key points:
1. I know how to do this, thanks to Iron Man building
2. Right now, I don't think our budget covers experimenting with the ideal answer of moulding and casting our own latex cowl
3. In response to the suggestion earlier, I don't want to buy one already made. Enough of this build is simple garment purchasing, and I want to feel like it has a personal touch. Plus, all the current cowls available would need so much modding that it would a) ruin the original cowl and b) be as involved as making my own.
So, we started off with the Captain America helmet, and aside from the dome shape of those original pep files, everything else has been freehanded. There were "scaffolding" struts secured inside to make sure the internal shape matched Sarah's measurements at the different points, such as the temples, below the eyes and behind the ears, and these were cut out again once I had coated the inside and out with two layers of resin, as well as two layers of fibreglass cloth inside.
Obviously, it's in need of body filler and sanding to get it looking like I want. Once it's up to spec, we'll be spraying it with plastidip in order to get that rubberised / latex look that suits the piece. Sarah is the sanding and filler master, so I'm handing it over to her for development.
Meanwhile, the yellow leather has now arrived, and Sarah is starting work on the gloves today. I'll post pictures of the garments once I see some progress to show off.
And finally, I thought I'd post another photo of the jacket in better lighting to illustrate the colour choice:

To be honest, even that is a bit off-colour, but you get the idea. It will all look great once it's finished and I have my DSLR to capture the greatness!