For most sanding, I use Shop Smith's "Film Finishing Sheets". It comes in P120-P320 grades, and is really fairly long lasting, The film backing does act a wee bit as a backer. It does NOT fold too easily with that backing film, so I cut it into smaller pieces for use. As for years I have used a 1/4-sheet random orbital sander, that is the size I still get. It is not real cheap, by any means, but as I said, it seems to last well.
Generally available at Lowe's in their hand tool area. Use double-sided tape to fasten it to a backer. It does claim to have an "anti-clog coating", and it seems to work well.