The grips are pretty bad home workshop jobs. Try this site for grips. While the URL points at wood grips, I think they also have the black plastic that mimic the old hard rubber.
http://www.gungrip.com/items_9__Colt...n%20Grips.html
I tried to find the plastic, but that web site is about the world's worst, even though their grips are very good.
I don't suppose I have to say this, but will anyway, being a $%^*&(. Do not fire that gun with .38 Super ammo and never fire it without the slide lock (the front key) in place. And do not try to drive the slide lock out; remove it by pushing in on the recoil spring plug.
Jim