You could, I suppose. Someone somewhere posted that if you trim an area in the current batter box, you can actually fit a much larger battery, albeit, still a power sports type. Hopefully, someone will remember the specifics...
Yes, This may be the best option for you.
There is not much as for a bigger direct replacement outside of a lithium battery.
But I see you are in a cold area so I would not recommend lithium.
Search in 700 forum. You can fit a YTX 20 after triming out original battery location. I will be doing it as soon as my current battery fails. Its 310 vs 220 cold cranking amps.