Hey Joe! Afraid there aren't a lot of options out there in true one weights!
Virtually all of them are high end...
First, let me ask what rod you want to put it on. An actual one weight may not be suitable in all cases. A one weight may actually end up being a bit of a hindrance in the long run!
To keep the cost in a more comfortable zone, a two or two/three weight might be more suited if the rod will handle it - and I suspect that most of these really light line rods can certainly do it!
Let me know what the rod is!