Talking seriously, I'd try cheapest windbreaker upon your leathers. Recently I've seen a guy wearing Joe Rocket Phoenix (nylon mesh with protection) and windbreaker. I've seen him on a Bay Bridge, and he didn't look like he was in cold.
I think you'd be pleasantly surprised. I sometimes wear a military issue rain jacket with a field jacket liner in it for work. We get some pretty cold winds out in the mountains and it breaks 'em right up. I wouldn't wear it riding though, the hood would act like a parachute and probably strangle me. My MSR jacket (dual sport type) is lined with some type of pvc or rubbberized stuff and it works great in the rain and really blocks out the wind. It didn't come with a liner so I also use a field jacket liner in it when it's cold. But just a thin wind breaker would really work good.