I just did something today that is, roughly, like this. The difference is that I am using an 8GB stick and I don't require an image. What I did worked for me but may be terrible for you depending on these questions:
1. how much space are you using on your hd
2 is having an img important.
That said, what I did was to unmount my stick and then:
dd if=/dev/sdx of=/dev/sdy bs=512 conv=noerror,sync
That I have formatted my 8G stick in full is grossly unnecessary and made it take much longer than it should have if I'd had the forethought to make it smaller.
Hey, it is one possibility.
P.S.
My first effort was to do what gerald_clark wrote but it did not quite work. Specifically, I noted that I did not have alsamixer on the new stick. Clearly, I made a mistake. I needed things to work without the additional problem solving, hence, my solution.