I can hear the grass growing …

You could find a battery of the same voltage and swap the connectors. I used to run my old electric on industrial video camera batteries.

There's a guy on the hillside, First Avenue East & Fifth Street, who sells rebuilt mowers.  There are always a number of mowers for sale outside his apartment lined up on the street where he does the work. His set up is a little odd, working out of the living room of his apartment, but he always has a lot of product for sale. He did some maintenance work on mine and was easy to deal with.

If anyone could rig that jury, it'd be Tim. You could, of course, go green and get yerself a goat.

Craigslist has several.