WOW those are spendy little batteries (but definitely tiny!)
The batteries I'm talking about were like $30 from wal-mart a pop... lol.
EverStart U1P-7 Lawn & Garden Battery: Automotive : Walmart.com
I'd be using one now if my current DD didn't have a scrap full size battery already in it... whenever it goes out, I'm sure I'll pull out the 'ol 1/2 sized battery tray and mount a new L&G battery to it.