barbeddragon still makes/sells hers
I used an xacto handle and a SIZE 24 embroidery/tapestry needle (yarnology brand if anyone cares), cut the tip off at an angle , sometimes cut the bottom to make the needle shorter too.
some needles last for several heads, others break a few holes in. sometimes it's the pony plastic hardness, sometimes it's the amount of hair I'm trying to do at once, sometimes it's the needles
just loop the midpoint of the hair over a finger and scoop it into the eye of the needle, and poke it into the plug hole. ta-da! I glued on the inside at the end for extra support, but if you're not doing a lot of brushing/styling you don't need to