I've also never been able to find it for sale anywhere. I searched every brand I could find, including Mei Mei. Its LISTED, but never in stock anywhere. The closest I got was a "marigold" yellow...which is a bit darker than the brighter yellow that works so well for me (a HUGE thanks to RickZ on that!!). And from Ebay I bought a "cone" of a yellow boa yarn that turned out to have shorter fibers than the Mei Mei, and doesn't work as well for me.

If you're interested in doing some looking on your own, PM me your email address, and I can send you a PDF I made that includes all the brand names I've been able to locate. You never know when the right item might show up on Ebay or at some fabric/sewing/craft store.