Depending on how deep you discharged it, you probably just need to charge it. But if you find you do need to replace it, the 9 Amp-hour version Vivo suggests is certainly the way to go.
I replaced mine after I'd stored the Super8 for months without disconnecting the battery. The light control box continually drained the battery - even with the key off - and killed the battery. The drain is only a little, but over the course of several months, it was enough to kill the battery). Anyway, the battery model# is (YTZ10S) and it fits fine, and works great:
http://www.amazon.com/gp/product/B004IUKTKY/As it turns out, it was also cheaper than the 7Amp-hour version as well.