Tomtom

I have the 5200, it wont bluetooth to your helmet but as long as you get a suitable mount and case it'll work fine.

 

I used my car's TomTom 5100 for a while with a handlebar-mounted case from RiderMount. If you got the angle right it was fine, which was quite easy with the joint extension I also got which allows another articulation. I still have the case if you'd like it for the price of the postage. It's one of these. My 5 inch smartphone fits it fine as does the 5 inch TT 5100. Drop me a PM if you'd like it as I splashed out on a TT Rider last year so the case is surplus to requirements.