I usually buy my sp dynohubs on ebay and they get shipped direct from Taiwan. I recently noticed you can now get them cheaper from Starbike. I got a SON through my LBS, who ordered it from Peter White. The only compelling model they have right now for me is the version that conducts through the fork, so it's a bit specialized.

I think it's pretty clear that the Supernova hubs are rebadged SP's. People were excited about SP's clutched version when Velo Orange was going to sell them, but then it flamed out. I don't see the need really, I typically run my lights all the time.