Hi,
Normally you can buy these batteries already with the pins attached to them.
Well I know where I can get the from. Then all you have to do is remove the
old battery and then solder the new one in place via the pins. I would also
recommend using a low wattage and constant temperature soldering iron. (Note
not all soldering irons are constant temperature). I am not to sure where
you are situated either so getting a battery with the pins already attached
might be a problem. As not everyone carries them. Best bet is to try a hobby
shop that has custom made battery packs for R/C cars, planes etc. Then see
if they can contact their supplier and provide you with the correct battery.
If all else fails let me know and if you are interested I could send you one
providing you are willing to pay for the battery and postage to where you
are.

Regards
Erica

I've got an old Flash Advance pro 256 and the backup battery is still going
strong. Is it a fault with the extremes or have I just been lucky ?