Good idea, I've got bikes and have used bike helmets obviously but eg the one I have now, the lens on it is pretty thick, cut/file/sand down the edges and it should bend enough and fix in? Can you post a pic of the inside please? Also love the colours and kill counts.
What about pinlock inserts? https://www.racevisors.co.uk/category/pinlock-inserts I've actually got a yellow one for my bike helmet and it has great anti-fogging on it. I'm going for a kinda republic commando look but not sure how a blue visor will look.
https://www.thevisorshop.com/en/LS2-FF399-Visor/m-22725.aspx
Looking at them and the mask it seems like the visor on the mask might be too tall - what are the dimensions of it fully before insertion into the mask, and what secures it in place?
Could even put some LEDs on the inside:
I sold a mint condition i5 on ebay for £120 the other day when I realised I couldn't use it with my helmet / headset, should have posted it on here.