i tried 尿片冰袋 last time. It worked. I went to Vietnam for 5 days. I asked the frontdesk to put my milk in freezer. all my milk become ice before i leave the hotel. the morning i left vietnam, i pumped milk but threw away cos there is insufficient time to freeze it.
from the time my milk left freezer to the time i returned home in hk, it took more than 7 hours. all my milk was still ice.
i used two 尿片冰袋, two normal 冰袋 and wrapped them in two layers.