I bought 2 car chargers from MonoPrice for a few bucks each. They turned out to be slow charging devices and wouldn't charge the Bionic.
Someone on here suggested these on Amazon - they are $3.64 each. I ordered two and they are FANTASTIC. The are rapid chargers and they are NICE.
Amazon.com: Motorola Vehicle Power Adapter micro-USB Rapid Rate Charger: Cell Phones & Accessories
I would suggest buying these before spending $29.99 from Verizon.