low power AM transmitter-any recommendations?

Can anyone recommend any of the low power AM transmitters that are available out there? I would prefer a kit, but if a particular pre-assembled unit is a standout performer, I would consider that one. I need to have enough range to at least cover a medium sized parking lot, so I can transmit period programs at our Antique Radio Club's swap meets. Any suggestions about transmitters and antennas would be greatly appreciated.

Thanks,
Mike