How do I fix worn out pressure pads in old cassettes?

Back in 1991 I was able to purchase cassettes from Radio Shack with no tape in them. Only the spools and the leader tape. I recovered several cassettes that had turned to crappy playback due to, what I finally determined, was simply the pressure pad not working properly. Now it is 2009 and again, some of my old tapes sound crappy. Where can one get "screw-together" cassettes like those old ones? You can see this item here on page 100 of the Radio Shack online catalog. Just copy and paste this to your browser.
http://www.radioshackcatalogs.com/catalog_directory.html
Can these be had anywhere? What is important is that they must be NEW. This is what I found necessary to replace the pressure pad in any cassette. It WORKS unbelievably well! Otherwise I will be looking to buy NEW blank cassettes and throw away the tape in them. But they should be "screw together" units. Any clues?