Go to your LBS and ask for a Sturmey Archer generic spacer. Or find a discarded SA hub and take off the cog (held in place by a steel circlip, just whip it off with a small flat bladed screwdriver) and chances are you will find such a spacer underneath the cog. I used two of these to get my chainline right. Mind you, they are 1,5 mm thick, so not very useful if you have to make smaller adjustments.