Like with many other single sided disk drives, when the felt pad gets missing, I would find an old cassette tape and remove the felt pad from the center Read/Write head; it is on a brass bracket, so with a pliers I would pull it the bracket with the felt pad on it. Then I would carefully remove the felt pad from the bracket and put it on the spot where is belongs on the drive. The trick was getting the right glue to use to stick the pad in place.

I saved many old single sided drives this way.