I just purchased a tiny little 6 vt. battery for my Express from a company: High-Tech Battery Solutions in Twinsburg,OH. The battery brand is Motobatt and they give a 2 year warranty and it's a sealed AGM battery.
They also have a pt.# MB12U which is also an AGM w/ a 2 year warranty that's equivalent to a YB12A-A and they want $81 shipped.
Have any of you tried it yet ? is that too much to pay ?