If you mean the original CAR-15 carbine stocks, like for a retro build, then your options are pretty limited without finding an OEM Colt or Stag Arms CAR-15 unit which are out of production.
If you can live with a knock-off, then M&A Parts sells a comparable "fiberlite" style CAR-15 stock body and complete buttstock kit that is basically the same quality as the unmarked Colt stocks in my experience. See here: