YTX9A should be fine.
For anyone else wanting to know stuff,
You need to think out question and give as much information as possible
It may seem perfectly logical to you but we are not mind readers.
Easy way to find out smallest reliable battery would probably find a modern sport bike with same or similar cylinder capacity.
in your case, a nominal 220cc.
Honda VF800 is close (4x200cc) what size battery does that use?
If that's too big for you, look at 750 sport bikes, they use close to the minimum size possible