~~~ they can pop up at any time after just walking in, prior, and that's why some pickers make their usual rounds several times per week along with even purchasing something (anything) from the shopkeeper or flea vendor... it makes and keeps them remembering you and what you're looking for. Still; the best results out in the field are from toy and paper stalls where chips are usually found in boxes of paper or in a box with remnants of board games and small toys... thus the reason why asking doesn't help too much unless one digs...