see the metal box idea.

if you've got a maplin in sheffield you could get a metal enclosure that would fit it i reckon and all you'd need to do is drill some holes in it and wrap the thing loosely so it gets air but with enough stuff that it'll be protected.

if you milliosn of people can bring back bottles of vodka wrapped in towels without breakages every year ims ure a metal box will be fine providing there's air.

you could attach some sort of tube that could stick out of the bag so it would definetely get air.