I've never seen low sodium kraut, but I've never looked. You could compare labels on different brands, perhaps you could shave off a few mgs that way. I would also check bottled and refrigerated brands, they may be lower too.
Rinsing will help some, but hard to tell how much exactly if you are counting mgs.
One trick I do with pickles is peel and spear fresh cucumbers, then soak them in leftover pickle juice for a few days. They get the pickle taste without as much sodium as regular pickles, but they don't keep as long. You might try this with leftover kraut juice, I would lightly steam the cabbage first to soften it a little.
You also might try to make your own, but I'm not familiar with the process myself.