I still can't find any concrete evidence, but several months ago this was a rather hot topic.
Some blue/greenlighters and I were discussing it, and one that SWORE his uncle was a cop lived and died by this trick:
Vacuum sealing a plastic bag with [drug] inside, then placing in another bag...also in this second bag would be large chlorine tablets...enough to cover the surface area of the bag.
He swore that this hurt the dogs nose and he would shy away from it...
"Of course if that's the case", I responded, "you could just use cayanne pepper". He didn't understand what I meant. I guess he never saw "Old Yeller".
Now that I think about it...
If you have access to a cop dog...Why not just take him for walks around the neighborhood...have him sniff out hidden drugs which you can then promptly...steal.