Re: ruger 22/45
Well you kinda answered your own question, fixed grips are not replaceable. Your stuck with what you got unless you use a wrap around rubber grip for a 1911. The 22/45 has the same grip frame as a 1911 but you would have to tap the frame for grip bushings for a 1911. You will destroy the value of the gun. You also have to be careful to not install them too close to the sear pin.
Only cowards shoot with their eyes closed....