I came up with the idea to do these about a year and a half ago. I'll share how I make them, but I better not see any up on etsy before I get a chance to post these ;) Anyway, I knit a little tube on dpn (about 7-10 sts on each of two needles). Usually I make one side completely stockinette stitch to glue the barrette back onto and do a 5 st cable with beads or buttons in it on the side that's for show. Well, I got that part working pretty quickly when I first did this. That's where I ran into a problem. I needed the tube to hold its shape and be a bit sturdier. At first, I thought of wooden shapes from the craft store, but then I remembered the curve of the barrette back. Finally, I figured out the answer. Are you ready for my secret ingredient?
Plastic canvas! I cut a piece of plastic canvas the same size as the tube, stuff it in and sew the end together. It's flexible, but still holds its shape! Sometimes I'm so smart, I scare myself. Just kidding. This is one of the first ones I made:
The scans don't show it very well, but you can see that the knitted piece follows the curve of the barrette back and it maintains its shape. It's held up for over 18 months so far! This is a great quick little project to use up quick yarn. You can do it as one flat piece, fold in half, and stitch along three sides if you aren't comfortable with dpns, but I'd rather struggle a little in the beginning and save a lot of time overall. Maybe that's just me.