You can get polymer clay at most craft stores, after it is baked it is slightly flexible but not brittle and can be filed, carved, drilled sanded and painted, It really is not clay but is called that because you can mold it and it will stay playable until it is baked, if you leave it out for several months it will dry out somewhat, but you can add a little vegetable oil and bring it back to life. It comes in many colors and also comes in translucent, and translucent colors, which will add depth to you finished project. From what I have read it done right you can make ivory that is hard to tell from the real thing. Most of the grip manufactures use a form of polymer to make their grips.
1. Get the translucent clay as your base then the other colors you want to add to it. The links below will tell you more about it and recipes, also hardware I use treaded inserts used for furniture, you should be able to get them at most hardware stores.
2. I used a old shoebox for the card board, lay your grips on it and trace the outside of the grips and cut the shape out this is your base to work on, making small holes in the cardboard for the screw placement and on a Remington for the pin placement.
3. mix the clay to your liking and start shaping it on the cardboard, after you get it ruffed out place it into the frame of the gun and continue shaping, once it is shaped fairly close make the screw hole bigger and push the screw thru both sides, it will naturally make the inset in the clay for the final product you may have to cut the screw if it is to long, take the screw out push the insert into the other side, than screw the grips onto the frame and finish shaping.
4. Take the grips off lay them on some aluminum foil bake them in the oven at 350 deg for 15 min then let cool, they will be very hot.
peel or sand the cardboard off the back. it will come off pretty easy, finish sand it, and final fit them and you are done. I used a dermal and sanding drum for most of it then a fine grade sand paper followed by corse sand to ad some grain to them. and a acrylic clear coat spray to seal them.
Note. Their may be some slight worpage when you bake them, if so nail some sand paper to a pice of wood and sand them flat again, if you over sand or make a mistake you can press in some left over clay and rebake it for 10 min and sand it back down. the links below will give you more info. You can also google making faux ivory, making faux ivory out of polymer clay, their are also youtube vids you can search.
http://www.wikihow.com/Make-Faux-Ivory-With-Polymer-Clay
http://www.desiredcreations.com/howTo_Desk.htm
http://sunnibergeron.com/crafts/tutorials.html
http://santafecreativetourism.org/2...ivory-beads-tory-hughes-studio-june-2nd-2012/
http://www.beadsandbeading.com/blog/polymer-clay-tutorial-faux-bone-faux-ivory-technique-video/7197/
http://en.wikipedia.org/wiki/Polymer_clay