small FM transmitter for mobile pirate transmitting

We want to get mobile with our pirate radio operation. Ideally we'll have 3 identical setups we can move around. Can any of you point us in the direction we need to start looking? Price is obviously a factor, but size and low power consumption are important as well, so we're prepared to pay. We have electronic nerds among us, and are prepared to do quite a bit of DIY to keep the costs down. We're looking for 30-50W FM in the 80-108Mhz band.

Our old mentor sold us his own stationary rig, which we've been using until recently, so we know nothing about where to buy kit covertly.
Any helpful hint and links would be appreciated.