This may be a few years too late, but seeing this now for the first time.
I was surprised to see that this plant isn't common, and that people don't seem to think about it! I found a vendor selling the fen nettle seeds on ebay, a guy from Poland. I believe his name on ebay is lupinaster. I have most of the seeds in the fridge to preserve them, but the ones I did plant all germinated and are growing well!
It does still have the sting, but its about 85% less sting. And the stings truly suck, so that 85% is a massive deal for any Gardener lol.
