At a risk of going off-topic; the cold-smoking attachment isn't the best way to cold smoke - being directly attached, it isn't exactly cold.
It is better (and cheaper) to build a separate box, and duct the smoke into it through a length of flexible pipe.
I did this for a while, but then went for a completely separate cold smoker, as the number of times I wanted to hot smoke and cold smoke at the same time were precious few. I now use the ProQ Cold Smoker, and love it.
http://www.macsbbq.com/cold-smokers