Hi Mark,
Most of the time named plants sold are mericlones of awarded individual plants. A grower decides to mericlone a good plant, then they are sold on the market for a while. After the first batch of mericlones is wholesaled it takes a while for them to be sold at the retail level.
In the future somebody might mericlone it again if it is a good seller, an easy grower, and demand is there for more.
A lot of times future hybrids wind up being better than previous ones. In this case it becomes very difficult to find old hybrids.
People see flowers online and fall in love with them. Realize online photos are going to be the very best flowers somebody could grow on that plant in ideal conditions. It might look a lot different in my house. And a lot of times people might find other hybrids more appealing if they only knew they existed.
With that in mind, here are some US nurseries that sell a lot of Phalaenopsis:
Homepage ⋆ Big Leaf Orchids
Orchids By Hausermann: Storefront
Phalaenopsis
There is a Vendor Feedback forum here on Orchid Board where you can get more information.