Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
Possible source https://www.amazon.co.uk/Black-Rubber-Channel-Edging-Trim/dp/B01N2OCLUA/ref=asc_df_B01N2OCLUA/?tag=googshopuk-21&linkCode=df0&hvadid=309954591991&hvpos=&hvnetw=g&hvrand=1408491796720562442&hvpone=&hvptwo=&hvqmt=&hvdev=t&hvdvcmdl=&hvlocint=&hvlocphy=9045911&hvtargid=pla-715926403159&psc=1 as general supply. I was searching through crash helmet rubber trim type things to find alternative. Types like Simpson have used this around eye apeture as example.
I have had a look about for a 750F1 air box to try a K seal on but, don't have one here mate, sorry