Overall, I must say that the Demenis Wildlife Park is the best place to pickpocket nobles. You can easily run off and re-join the crowd without any issues. I have 5 bars now in just a couple hours of work. It makes for an easy rotation for a quick break from work.
Here's a quick screen grab of a visitor with bars since I had a tough time finding one. It takes some time but be patient. Grab the bar, run off, and come back for more (make sure to save your game after you get one). Quick note, I did manage to get 2 bars from one visitor. If you look closely, you can see that some have stacks of 2 or 3 bars. Apparently, you can get more than one - quite the haul! They appear to either be carrying a copper pouch, a quill or perhaps a key, nothing, or 1-3 gold bars.
I can't say what the refresh time is for each visitor getting new loot, only that it's not long. I make a round and come back, and they seem to have changed. Maybe I should just stand next to one and keep scanning over and over to see if it's different each time. Perhaps it's an RNG each time you scan someone. My results so far from attempts only on people with bars are cheese, jade, 1-2 gold bars.
My guess is that what they are carrying changes every 2-3 minutes and lasts a few seconds depending on what it is. If you see a bar, grab it quickly or you will end up with a random item. I think the longer you wait (taking screenshots) the less chance you have of getting the bar.
