Ivory is near impossible to get. Mother of pearl has been widely used by real western gunslinger as well as ivory, bone and antler. The standard gun grips were wood and hard rubber and during WW 2 plastic was prevalent.
I have a pair of 1890 top break Nickel plated S&W pocket pistols one has nice mother of pearl grips these are in the anemic 38 S&W caliber(not to be confused with 38 Special ) . These as Patton said in the movie of the same name carried by Pimps and gamblers. But also by anyone who wanted a concealable weapon with fancier than plain wood or hard rubber grips.
If Patton actually said the line. It was probably to ruffle the feathers of the news media who he despised. As all good soldiers should.
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Interestingly, I have a fairly large number of whales teeth, and a bit of whalebone. The teeth are essentially identical to ivory. This was all acquired by my parents in the early ‘70s before the embargo on whale products. At this point, it is virtually impossible to sell this stuff across state lines, even though the animals died long ago and the product was brought legally into the country. But you know, I’m pretty sure that I can find someone somewhere in Texas who does artwork with handgun grips to carve some of those teeth up and put it on some of my handguns.