When I and my dealer were looking for them last winter, Sunwize was the best supplied distributor, but I haven't looked in the last four months.
Sunwize doesn't sell retail, and they only sell complete packages with inverters. There's a dealer contact form at
http://www.sunwize.com/buy/dealerconnect.htm . Some of the Internet stores sell Sunwize packages too.
So far, my Sanyo 190's are great panels. My system rates 3040 watts output, according to the California Energy Commission test ratings. Today I was over 3100 watts for almost an hour, with a peak at 3180. This is with three strings, two facing 160 and one facing 250, paralleled on the same inverter.
They are also the most space efficient panels I know of, and they are high voltage so the strings are shorter, giving more layout flexibility.
That said, they are hybrid technology so some people will question whether their output will last. Sanyo had some graphs that showed them just about constant over three years, but time will tell.