http://www.the2buds.com/surs6x9.htm
I believe that I bought mine here.
There are also penny sleeves that are supposed to fit inside the 6 x 9 toploaders, but they don't fit. They are about 1mm too wide for the 6 x 9 holder. this is why I use a 5 x 7 penny sleeve inside the 6 x 9 toploader I linked to above.
Alan