x-nyc mama,
not sure if you're still looking for milk storage bags, but i am using the ones by Lansinoh (these seem to be the most common in the baby shops in HK) @ $54/25 pc box. i usually get them at bumps to babes in central, but i think they are out of stock this week. might want to call ahead and check if they have received another shipment.
alternatively, medela also has milk storage bags, but i think they are ridiculously expensive ($129/20 pc box)