These are the 20AH cells you want. They come in 12v packs. So 12v x 3 packs = 36v which is about $384
http://elitepowersolutions.com/produ...products_id=74
You've have to wire it up yourself but it's not hard. I went to lowes and got about $15 worth of 10 gauge wire and some connectors from Radio Shack...you can also get the connectors at Lowes or Home Depot or Menards or any hardware store. Take the bolt from the battery with you to make sure the connector fits over the bolts. The connectors are called "Ring Terminals". I didn't even use a crimp gun, I just used some pliers with mine and it still holds up. Then I took all 3 12v packs and wrapped with duck tape so they wouldn't come apart while I was riding.