Chip McCormick thin grips
I just bought a set of Chip McCormick thin grips in rosewood from CDNN in Texas for my Colt Commander. They came complete with the short bushings and screws needed to install them.
The improvement in the concealability of the gun is remarkable - they seem to reduce grip thickness by about 0.2 inches, and the gun is absolutely skinny now. It is the usual 0.9 inches thick through the slide, and only 1.1 inches thick through the grip panels. It is not as thin as my Walther PPK, but it is getting close. I really like them. I think they are an essential for any 1911 that is going to be carried concealed.