I bought mine in an art supply store that my next door neighbor was manager of. I showed the old stuff to her and she said "yes we have that in stock"
If I remember correctly it was about a dollar for a 24" X 30" sheet. There was just enough headliner material leftover from the sunroof opening to cover the visors, so my total cost was Cdn.$1.00 or currently US$0.845.
My problem was after I had my sun visors recovered I wasn't able to find anyone who could replicate the factory stitching, so I went with headliner adhesive like newer GM vehicles.
Old Visor and Patterns made from removed cloth

Finished Drivers side up

Finished Drivers side down

Finished Passengers side down

There are two attachment studs on the back of the mirror. I placed the mirror on the visor through the mounting holes. Then I put a thin brass (so it wouldn't rust and stain the cloth) washer over the stud. The stud has a head on it so I used an appropriate sized circlip to lock the mirror in place.
[This message has been edited by Tinkrr (edited 01-06-2009).]