I have only good things to say about my Wilson Combat 22 conversion kit for a 1911. It is as accurate as a typical low cost 22 full size and about the same price, plus it fits all my 1911 leather. Another up side is you can practice draw and first shot placement with the 22, and then change over to the 45 when ready. Because you use your 45 lower the trigger pull remains the same also.
I have also seen 22 conversions for the Beretta 92, any others out there I don't know about.