There's one for sale in the Trading Post Forum that comes with both counterweights and a backing plate:
http://autopia.org/forum/trading-pos...6-pc-sale.html
I think you can also get them on eBay and
Coastal Tools still sells them.
Back in December one of the three local Lowes had 4 in stock. I bought one as a spare (they price matched $47.60.... but only for one) and not long after that the other three were gone.