Here are two possible solutions that mount to the inside of the windshield,
~$20:
I know they aren't DIY, but hey, only $20, could save a lot of hassel!
Universal Am-Fm Hidden Windshield Antenna : eBay Motors
Interior Antenna AM/FM glass mount Road Rage: eBay Motors
Other possible solutions by Googling, "inside car am/fm antenna".
Good luck!