Cassette tape adapter + Cigarette lighter plug for power.

Alternatively.... walkman-style headphones connected to the empeg's line-out RCAs in place of the cassette tape adapter, you'll probably get better sound quality than the factory speakers in a rental car would give you. In some states it is illegal to drive with headphones on, though, so...

tanstaafl.

"There Ain't No Such Thing As A Free Lunch"