I can't remember where I saw them, although I know it was via Twitter and seeing someone tweet about them!
You can get these bad boys on www.amazon.co.uk, however they are pretty pricey at £30 each! Oh, here they are...
You can get an Iron Man, Captain America, Thor and hulk USB stick (the two I haven't got are on my birthday wish list [12th Sep] - although I'm not entirely sure I need them it'd be nice to have the set!)
I have used the Iron Man one for all of my teaching resources and have used the Captain America one for my DJing (I load up all my songs on here and I can then plug straight into my CDJs!! The USB stick I have been using this year on my GTP has all of my GTP lesson plans and will be where I save all of my NQT lesson plans, admin files etc. This way I don't have to rely on just one USB stick to contain everything I need. Everything on both sticks is already backed up on my computer too and I've got into the routine of backing all my data up every month (and even this makes me feel like that it isn't enough).
I love getting everything organised, and it was amazing how many resources I had accumulated over the course of my GTP year - many that aren't even on the USB sticks and are in various shared Dropbox files! It should mean that I am FULLY prepared for the unexpected and should be able to just bring up a resource when needed if my lessons change direction or I am put on cover at the last minute etc.