They are usually only avaible from PX's etc. If you are in Germany give the one in JHQ a call and order one from there. Otherwise, wait til you go on ops, even then they arent that easy to get hold of. You usually only get them on 1033 for the duration of your tour.
They're available from the PX at JHQ as Mag-to-grid says, for approx 12 quid.....I buy one every time I'm across there, fill it with US goodies, beer and duty frees and bring it back with me (never exceeding any limits on booze or fags....)
The spacecases are a bit expensive, but they come with my personal reccomendation
They would be ideal for deployments - they are basically individual comfy boxes. I wish I'd had one for my Iraq trips, chuck your laptops, DVD player etc. in there and even if the ship sinks, they'll stay dry - probably...
I reckon they'd be worth a Gems suggestion for issue to individuals on their 1157 or UNICOM equiv.