I have researched the location of the 35 largest Swiss chocolate manufacturers in Switzerland (there was a French company that snuck into the list I was working from, but that is not within my rules). What I found was that boston_jen may well be correct about where the chocolate task is located. Here is what I found:
the largest number (4) is in Basel
there are a few in Geneva (3)
there are many scattered all around Switzerland
there are none near Zermatt (the closest appears to be Nestle several hours away by train or car in Vevey)
there are 3 in Zurich and 3 in its suburbs, making it the highest concentration
I believe that based on this information, the pit stop for episode 10 is likely to be in the Zurich area or maybe the Geneva area. Basel is out due to the extra time to reach there and the plane schedules being inferior to Zurich.