Well your best bet would be to go to a battery store and have them look up a battery that will fit in the bike or match the dimensions of the old battery. I know I could go to a battery store chain here (
Batteries Plus) in San Luis Obispo and they would look up what I needed and it would be cheaper than a Yuasa. As long as you get a battery tender type charger (
I prefer the Noco Genius chargers) on it then you won't have any problems for a long long time. You could also call Yuasa and ask them over the phone if they could look up a battery that has the dimensions you want and they would probably help you out. I've never seen a 12V in that size but you can buy one that's not as wide and it would work without a problem.