I have a bootable USB-drive with one partiton. The drive is 16GB and the partition is 32 MB. I'd like to create an ISO of the drive (including the boot sector). Using dd, I can either create an image of the partition (which would be 32MB large, but is not what I want, because it won't be bootable) or I can create an image of the entire drive, which would be a huge waste of time and disk space. I tried using clonezilla, but I wasn't able to create an ISO from a clonezilla image.
How can I create a bootable image of my drive without imaging the entire unused part of the drive too? PS: As long as the image is bootable and can be used in virtualbox, I don't really care if it is an ISO or not.