The 26R battery is the right size with the top terminals reversed for proper orientation (negative closest to firewall and terminals on the left side). You can get a 525 cca battery at Walmart or Runnings for about $80.
Car batteries make good replacements if the right size. If it poops out in a tractor, it’s not as much of a problem as with a car..
If you use a trickle charger when the tractor is not being used, your battery will last a long time. I had one last for nearly 20 years because I religiously looked after it.
Be sure to use a battery tray and secure the battery with the clamp on the bottom to avoid leakage. Use a maintenance free type battery.
