You can order both from Peter White wheels (This is where I obtained mine):
http://www.peterwhitecycles.com/
Peter white web page on the Schmidt:
http://www.peterwhitecycles.com/schmidt.asp
Photo of the SON in Red (Mine is in Silver, it is also available in Black):
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If you decide to go with a generator, wheel "barrel" generators (The ones that run off the tire) are NOT recommend, the snow and other junk common in Winter weather tends to make them non-functional. I have heard no complaints in that regard with Hub Generators and I have had no problems in that regard.
As to my SON, my first SON lasted about 5-6 years (it only had a three year warranty) so I had to purchase a new one about 6-7 years ago. No problem with the new HUB, but like anything mechanical I do expect it to wear out but I run it constantly (i,e I never turn off my lights). When I first purchased my SON, Schmidt did not have LED headlights, LED Taillights but no LED headlights. I therefore used a regular Schmidt headlight. I have since switched to LEDs, the first one last a couple of years, then it was damaged (I am rough on things) and I had to purchased a new one. The only problem I have had with them is tied in with the wiring. You have to make sure the wires are hooked up to the lights and the generator. No hookup, no lights. Given the SON is an AC system, you have to make sure BOTH lines are connected.
REI does sell the Shaman Generator, it is considered second best to the SON, but still a good generator.
The problem is you either have to buy a new wheel with the HUB (Which is what I did) OR install the generator yourself, by removing the present hub and spokes and installing the Generator HUB and new spokes (Much shorter spokes for the Generator is that much more around then a normal front hub). Given the price difference Peter White charges, I would tend to go with him making the wheel up but it is the buyer's decision.
Peter White also sells Sanyo Generators, higher drag then the Schmidt but a lot cheaper:
http://www.peterwhitecycles.com/sanyo.asp
Peter White also sells Shimano Generators:
http://www.peterwhitecycles.com/shimano3n70.asp