I've used Heidfeld's one for few seasons now.
Can I possibly get Prost's 1985 helmet?
http://www.f1-helmets.com/alain-prost-1985-replica-helmet-p-51.html?cPath=32&osCsid=debda72a914da3e4bb1c233292faff07
http://www.google.co.uk/imgres?q=prost+helmet+1985&um=1&hl=en&client=firefox-a&sa=N&rls=org.mozilla:en-GB:official&biw=1366&bih=575&tbm=isch&tbnid=ISMWLnXfTJ0PTM:&imgrefurl=http://www.f1-helmets.net/prost-alain-helmets-alain-prost-1985-helmet-replica-laren-p-394.html%3Flanguage%3Den%26currency%3DUSD&docid=k-Z3JTtyMszsfM&itg=1&w=672&h=766&ei=2QmTTvaDLpSy8QPEoKkU&zoom=1&iact=rc&dur=437&page=2&tbnh=165&tbnw=145&start=21&ndsp=10&ved=1t:429,r:8,s:21&tx=115&ty=60