Sunpower tends to sell only through dealers and they are doing large scale land installations - think by the pallet. You may find a dealer who has some left over panels
from an order. There are many suppliers of panels that are made with Sunpower cells. So if what you want is the higher efficiency, then these are easily obtainable in both flex and rigid panels. You can get low cost ones off of Aliexpress from many different suppliers, or buy the higher end ones directly from US sources. I believe the Solbien panels are Sunpower cells and available in the US.