buy a $3.95 battery hold down bracket
you need to make sure it has a thin rod and metric/small thread
you'll also need a 10mm nut , and a 12mm nut ( a welder is also handy)

ok , now you can see the 10mm nut has been ground down , use a grinder , or a bench grinder for the task (make sure you keep it rounded)
It should be the same size as the pin for maximum effectiveness
Now weld on the 12mm nut down towards the bottom of the rod (as per pic) if you dont have a welder , stop into a welding shop and ask them if they can quickly throw a weld on it , shouldnt cost you anything for them to do it
and if you had the original pin removing tool you can still use the steel bar used to hold the original pin while you belted it with a knockometer (hammer) If you dont have this tool , get a 12mm metal rod with a 7mm hole drilled in the end to go on the pin remover.
im on my 2nd one , the first one outlasting my original $40 tool by about 40 doors