Do they make custom grips for a Miroku liberty chief 38 special revolver?

No. The Miroku .38 series of pistols are their own creation that took on the best features of both Colt as well as Smith & Wesson made firearms. For example, the 4" barreled "Police" version has a grip frame which is larger than a "K" frame S&W but not quite the same size as the "N" frame either? Colt, nor Ruger grips will fit its contour either. Your best bet is to play around with a "close" fitting S&W style set of grips and modify it in some way to fit.