HI terryc ,
 How about  this . A rechargeable cell box that with  NiMH technology that you can wear with  your wireless rig. You could phantom power your Bass with it .The design is in my mind , but could be rigged up in a jiffy! . You can try this at home ! check it out .

Sonicus, I have seen somethink like what you are suggesting before and was just now trying to look for it but can't find it.  
If I remember correctly you it supplies the power down the jack lead to the guitar but I think it is a stereo lead of some kind.
 
Jazzyvee

Ok Found one..
http://www.guitarelectronics.com/product/PMTXBAT9/9-Volt-External-Battery-System-for-Active-Electronics.html

YES jazzyvee .      
 
                   I believe you have found already in existence what I was thinking about. I think EBS offers a 9 volt phantom power feature in some of their products as  well .That is a useful link that you have provided, thanks .
 
       Sonic Regards !

I think that box would be even better if had a socket so that you could plug a boss 9v pedal psu into it as an alternative to batteries.
 
Jazzyvee

I agree as I often use connect-ability as the criterion in
the decision making factor of an equipment purchase. Versatility is virtuous!