Distribution has become difficult since KWD has been having financial difficulties, so I don't think there is a current US distributor that can get things reliably for Noblex, and same for Robert White, which used to be a Noblex distributor. Calumet and Photo Habitat were Noblex dealers, so they may have a few odd items. RTS was the US distributor, but I gather that RTS has dropped them. I've been scavenging Noblex filters on eBay. There's a #11 filter on eBay right now, if that's one you are looking for.
Mine, which belonged to Ted Harris, has three focus positions, so I've calculated DOF charts for the lens and for the two closeup lenses (which can't be used together easily), and I bought a tape measure that I've marked with the optimal focus distances for all three positions with the main lens alone and with each of the close up lenses. I've attached a table that I have taped to the back of the camera with the DOF chart for the main lens in the three focus positions and the optimal focus positions for the main lens and the two closeups.
Recently someone was selling lots of filters and closeup lenses for Noblex on eBay, and they had +1, +2, and +3 diopters, which must have been special order or custom items. I think it would be very difficult to work with those lenses, because of the short DOF and the necessity of having semi-circular compositions for the whole panoramic subject to fall within the DOF range.
It makes astonishingly sharp images. Because of the swing lens design, sharpness doesn't decline at the extreme ends of the image, so it doesn't go soft where you would expect it to.
Here are a couple of Noblex shots I posted to flickr--