I did a quick Google check of the rubber bugger legs, as others prob have. It appears the Montana Fly Company (MFC) sells the material, though none seemed to be formed onto a wrap to create a hackle-style material. Rather, it appears to be various colorations and thicknesses in strands.
However, according to its Web site, MFC sales are restricted to retailers, and it has no listing of any PA retailers.
I don't know if it's the same material, but a suitable material is found as hair on inexpensive "troll" dolls. It's relatively fine and for me makes a good wrap for black fly larvae and caddis pupae. Some fabric stores also carry some materials that appear to be made from the same or similar material, which I assume to be a silicon "rubber".