Nettle seed from Finland.
I was teaching up north this week and found a supplier of nettle seeds.
He's got nettles (Urtica dioica) in all forms (dunno about roots, though). Seeds? No problem. Leaf? No problem. Boiled and frozen? Sure, how much did you want? ... and it's great quality, too. He's Matti Veijola; his email address is matti.veijola, something curvy goes here, armatti.fi. Mind that last dot, too. I'm not quite sure which languages he speaks, but you could try Finnish : )
Another guy, Pekka Heikkinen, distils Japanese peppermint (Mentha canadensis) into a divine essential oil, much sweeter than the peppermint (Mentha x piperita 'Mitcham') which he also distils. A cook who saw that we were in the testing kitchen came in and wanted more of the Japanese mint oil he'd gotten a couple years earlier: "3 drops of this to a kg of chocolate, mmmm!". I asked, dark or light chocolate, he said it doesn't matter which, either work. His (Pekka's, not the cook's) email address is pekka.heikkinen, you know what, mtt.fi.
Both do top quality stuff. Buy some if you're in the EU, you won't regret it.