...I bought a lightly used set of Pachmayr Presentation grips for my son's 1951...he prefers the bone that came on it...wanted Compacs but they're not made for that model...
...look at Pachy's website and go to revolver...then select colt...and on the right select pre-1971 Det Spl....long grip frames...and you'll see them...his is a second variation type frame...and they fit well...

http://www.guncollectorsclub.com/detective.htm


...if you need them, PM me and I'll send 'em to you...we won't need 'em 'round here...