I think you need this
http://www.sjscycles.co.uk/brompton-...0c940676ed6c33

I'm also thinking of going fenderless for summer, I live in San Mateo, and commute to Sunnyvale, usually Caltain Hillsdale-MountainView, sometimes I ride evenings all the way, through Palo Alto very close to Charles Wasson's place. PM me if you want to go halves on the the postage for a UK order.