Lock & Locks https://www.amazon.com/Water-tight-Storage-Container-HPL931/dp/B00GWZJJPE/ref=br_lf_m_atukbysne93z64e_ttl?_encoding=UTF8&s=kitchen These 3" palm-size round Lock & Locks (100ml, size:small) are big enough for geocoins or small trackables (plus a small logbook and cut down pencil).