Thinking about it, even if I did have a pinout I couldn't use it anymore as I removed the external port section ages ago so have no way to trace the pins back!
Yes, the unit in my pic needs 3v (2 x AA's). If all the system does is just save hi-scores then it I don't see it as being of much benefit - I didn't know if you could save game progress on the fly instead. Never mind!