Andrew, I would be really surprised if they went to the lengths of installing the other connectors and aerial lead and no power supply. Is one of the leads going into the block connector a 12v supply?
Not sure if it helps but the radio feed is on the same circuit as the horn via a 10A fuse.
If you really cant find one I'd run one myself with an inline fuse, the feed ought to be under ignition so you don't inadvertently leave it on.
I'll try and poke about a bit on mine later if it helps.
