actually  6  D  batteries  the original  box had an  adapter cable  but   Iam not the original owner   so I need to get one or make one

I have a  original Big Hauler90-0100  great  condition  but  only  runs on D battery  need the adapter cable  to use  rechargeable  7.6  V  battery or  a schematic  that  shows  the pin outs  for the cable  so  I  can make one