Here's an aftermarket pickup system which is designed to operate on phantom power if desired.
http://www.schattendesign.com/artist_preamp.htm
Notice that you need a special cable, CAB-1, to use 48v phantom power off a mic output. That cable has an XLR connector on one end and a TRS 1/4" plug on the other end.
They also have an 18v outboard power module (takes two 9v batteries) available if you want to power it with that way.
Gary