This shows my age, but, what the heck! I still have one from way-back-when and it stills works, although not as a seam ripper. I use it to clip articles/coupons/etc. from paper sources. It's called a Clipit. Here is a site where you can get one or more at only $1.99!
http://autopointinc.com/autopoint/ti...pit-96023.html
I just tried it to rip a seam. It doesn't work very well, at least for me. I think the blade is much too big for the stitches. Maybe it's just me . . . . I'll just stick to using it for paper clipping.