You can pick up a decent digital scale from any major department store in the kitchen supplies area or any of the office supply stores (tend to be postal scales). Usually between 20 to 40 dollars or thereabouts. The one I have is the 7001 DX and I just love it. You can find it at these two online suppliers or heck even check ebay for it.

http://www.reptilebasics.com/My-Weig...l-p-16191.html (I think he includes the batteries and the AC adapter in his pricing, a very good reliable supplier)

http://www.oldwillknottscales.com/my-weigh-7001dx.aspx (AC adapter extra)

Personally I've never bothered with the AC adapter. This scale doesn't eat up batteries at all.