The size of battery metal contacts is 15 x 13 mm , thickens 0.8 mm 

A dry wall metal supports are good alternative for metal sheet , for contacts.

A wood screw betwine  20 - 30 mm depends on tool handle size on the other side , for securing to tool.

Solder metal contact outside of plastic adapter and then insert in print . A 60 Watts or higher soldering iron is a good idea.

Some tools need a third pin that detect battery temperature , a work around is to use 10 000 ohms ( 10K ) ¼ Watts , connect betwine signal wire third one ( middle connection ) and battery minus usually, some use plus connection , so try with which one works . it is a 10 000 ohms resistor very very little chances of shorting something.

Once inserted a 3d printer pencil or a glue gun are good for securing connections.