Hi Will, Congrats on getting a JP. Would like to have one myself.
For my Panther and Sherman I use Universal Power Sport battery, UB22-12N. This is a 12Volt, 22 amp hour, sealed AGM type watercraft or motorcycle battery. The sealed AGM is nice as it can be laid on its side and not leak electrolite acid. Also requires no filling or open cells.
A wheelchair battery will also work. You want high amp hour capacity to enable long run times.