Ian, since you're in UK, getting a proper thingy from Paramount Cords in the USA might be expensive...
Anyway, I was just waiting for the right opportunity to show off my latest DIY gizmo - just what you need
Costs almost nothing to make - just a little patience. Doesn't look pretty, but works - and that counts (as you can see from the fancy lens cap, I don't care much about the looks
).
In short, it's a power connector from a PC computer - like the ones connected to hard disks, CD units, etc. Open a PC, and you'll se what I mean. Getting one shouldn't be a problem
Denis