Battery for a 89 Yamaha Big Bear 350

I have a 89 Yamaha Big Bear 350 and the battery has gone bad.
I am going to get a new battery for it but want to get the largest one I can fit into it.
I have been looking at lawn tractor batteries and wonder if one of them would work better then the stock battery.
They are larger and actually more affordable then the stock ATV batteries are.
Has anyone tried a different battery?
Did you go with a larger battery?
Any idea what the largest battery I can fit in it would be?

Do you have other recommendations?