If it’s the self contained model look for an Interstate SP-40. It’s 340 cca which is a little more than the standard lawnmower battery. Be sure you have a good size gauge on the wires connecting it all. While mine is not self contained I use that battery with some longer welding cables. It spins over everything from a yammie to a 250 single with plenty to spare. Maintain it properly and they are good for 2 to 3 years.
Interstate battery part# SP-40 or it’s equivelent.
Batteries are like tires. You get what you pay for.
Compare the cca’s (cold cranking amps). The higher the better.
You might also try at Walmart or Tractor Supply.
Look into Shorai lithium ion batteries. They cost a bit more but you can find good buys on ebay. They are very light, pack a punch, environmentally friendly, fast charging, and hold a charge for over a year.