The stock battery is just 2 x 12v 8ah. You could get 2 x 12v 12ah Batteries off amazon for about 55$. Just take the top off the old battery and scavenge the wiring from it.
https://www.amazon.com/ML12-12-Battery-Terminal-Mighty-Product/dp/B088TVX8MK/ref=sr_1_5?crid=3753A12BAHFZ9&keywords=12v%2B12ah&qid=1652790809&sprefix=12v12ah%2Caps%2C90&sr=8-5&th=1
I'd recommend getting a good 24v charger to replace the stock one as they are usually crap and kill batteries early, and take forever to recharge.