75AH 12V leisure battery for a disabled persons powerchair. (Wigmore HR6)

One of the batteries on my husbands outdoor powerchair has died. These batteries are as big, if not bigger than most car batteries, but built differently in the way they give out their energy. Hence why I need a leisure battery. I need one that is 75AH. Or, if you have a working pair of these of 65AH or higher I would be grateful too.