This what I used, https://www.amazon.com/gp/product/B0002262DK/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 I would wrap it in my sleeping bag to keep it cool. If I stayed at a hostel or albergue that had a refrigerator I would put it in there. I was able to time everything that I only took one pen, it worked out fine. Where are you planning on going? We did the Camino de Santiago/Portuguese coastal route