Hi, might be old news but anyhow....
Some time ago I bought a dry bag from Ebay sent form Korea. I was a bit dubious at first if it would even turn up but it did and it's awesome. So much so I bought another some time later. The delivery is quick - no more than a week each and no import charges 
This same bag sells on Alpacka Raft site for $90. 348 grams by my works scales and that's all i'd use to carry my gear in when on the river. the marines use them on their own or as a pack liner. I have a lighter waterproof Sealine 60 litre bright orange bag but it's not as rough, tough or as stealthy as this one by a long shot.
This bag apparently is available to the military in two flavours with the difference being with or without the bright orange safety colour inside that can be turned inside out for emergency signal. The one on Ebay has no bright orange
(well mine didn't) but this is normal and they are definately a proper USMC ILBE SACK SEAL LINE WATERPROOF DRY BAG 65L. The bag also uses a valve locking system to squeeze all the air out of the pack. Imho it's a bargain espcially for about £20 delivered.
anyway folks, just wanted to pass onthe info. If you want a top notch lines or dry bag you can use 'as is' that is rugged as hell you will struggle to find something better than this imo.
seller is sangwook790 and the item number is currently 330755179922. Appears to have relisted recently as before they sold well over 100 to satisifed customers, check out their feedback seeing how many they sold and the great comment, like you should if buying from ebay, and enjoy your top bit of gear
ta.
Edited: 29/06/2012 at 11:43
