Are you looking at real cold smoking (below 20 oC or so)?
I use a pro-Q cold smoke generator. A very cheap and easy option, but it depends on the outside temperature.
Actually, all cold smokers do, more or less.
A full CSG gives me about 10 hours of smoke at a maximum of 1 oC over the outside temperature.
I can only cold smoke at night in the winter.....
After smoking at night, I move the meat to the fridge and if it needs more smoke, I smoke again the next night