Yay -- I was (belatedly admittedly - sorry, as I thought you were sorted yesterday) about to post the details on my adapter. It IS 12V 800mA output.
In my experience if they're really, really dead the batteries barely get you started, so 5 minutes sounds like you might coax a bit more out if yours by ignoring the green light and reaseating. Good luck! 
Hi
Every cycle takes a little longer to charge, and gives Goofy a little more time to see his new home environment, its currently taking 45 mins to charge, and he lasted 10-15 mins on his last run !
Still not long enough yet to allow me to get to know him, and so the egg battery option is still on
I am looking at UK ebay sales at the moment for the egg due to the price, as I have recently been stung £20 on a £50 USA purchase - and how Royal Mail can charge £8 handling fee to simply push a postcard through a letterbox is beyond me
If I cant source a UK battery, then I will buy from here from RWM, I have quite a shopping list building :-)
By the way Goofy is far more cute than the youtube videos give Pleo credit for, also my biological pet seems to like him too, whereas Aibo frightens my cat off!
As I have a wooden floor he is managing to cover quite some distance, and I think as he has been in hibernation for some time he is very keen to keep his leaf in his mouth, and is making enough noise to ensure I know that he has arrived
Cant wait to try the skits from this site, I have them all downloaded, and ready to go, just need an energetic dino to take advantage of them
cheers
Stephen