I stole Devaclis' idea about mounting a Cigarette lighter for a power source, but then I wanted to take it to the next level...
After figuring out how to build one, I did a search and found this.

Didn't see it posted here yet, and I know most everyone who rides further than the next bar could use one of these, so enjoy!

I just ordered one so next week I'll update with how it works (and if it fries my phone).