you can only buy PUGs from the company. they aren't sold retail. remember, these are custom-fitted for your popup or hybrid.
you can buy solar blankets that are a standard 5x7 size. they are available from Cabelas, REI, Campmor, Bass Pro and they are also available from a number of online places.
they are also called all-weather blankets or sportsmen blankets. they sell for around $14US.