If you want a lithium type battery, I recommend Shorai.
Had one in my FZ1 and never had any problems.
A while ago, they largest capacity was 18 Ah, but now they have a 19 Ah.
For street use, I'd go with the largest capacity available. Still only weighs 2.2 lbs.
The 18 Ah is $189 and the 19 Ah is $199.
If you can't afford a lithium battery, then I'd recommend a good quality sealed, no-maintenance Absorbed Gas Mat (AGM) type lead-acid battery with 12 Ah capacity that fits the dimensions of the battery box.
Will be much heavier than a lithium (approx. 10 lbs vs. 2.2 lbs), but will be a bit cheaper.