I got this one from Costco a couple of years ago, it can change the unit.
http://www.google.com/products/catalog?hl=en&q=mail+digital+scale&cid=13838093089428887824&ei=f2x9TL6dGpeKywWNrOTsDg&sa=title&ved=0CAcQ8wIwADgA#p
http://www.google.com/products/catalog?hl=en&q=mail+digital+scale&cid=13838093089428887824&ei=f2x9TL6dGpeKywWNrOTsDg&sa=title&ved=0CAcQ8wIwADgA#p