Just got a new seam ripper: the Seam-fix. The actually seam ripping end is much smaller in blade thickness. The cap has a silicone top to just lightly rub away the threads you have ripped.
I like my Clover but it doesn't have a cap, so I enclosed the top with part of a straw. Hey, it works.
I also have some folding seam rippers from Germany. They fit nicely in my pocket when at a retreat or sewing with others. Haven't lost one yet. I forget who sells them here.
I bought a very fine bladed round file that I have been using to keep my Clover seam ripper sharp. After so many years it did finally need some attention. It worked.
ali