I've found a few basic ways to do this:
1) Use a standard non-isolated RS-485 transceiver, and isolate the data/control lines going to it with 6N137 optoisolators.
2) Use an isolated transceiver.
With either of these methods you have to provide isolated power to the transciever chip: a) use a small isolated DC-DC converter b) use a small transformer (P/N ??)
9600 baud, 300' distance
Any suggestions or alternate methods? thx