I'm not involved with this and its located at Simpson ltd. Colt conversion unit to .22LR.
http://www.simpsonltd.com/product_info.php?products_id=15871&osCsid=bd7ef997c995904f077f924abd748e2e
http://www.simpsonltd.com/product_info.php?products_id=15871&osCsid=bd7ef997c995904f077f924abd748e2e