This page has some FM transmitters for sale. To be sure what's legal, you'll need to find out from the FCC the rules and regs, Good luck searching the site at http://www.fcc.gov .I tried briefly and it's summaries are terrible.
_________________________
Dave Clark Georgetown, Texas MK2A 42Gb - AnoFace - Smoke Lens - Dead Tuner - Sirius Radio on AUX