Someone else beat me to the Ruger site reference for replacment wood grips--give 'em a try. (For 50th .357 and .44 Sp folks, you'll want to look at the various New Vaquero-referenced ones, wood and faux ivory, same frame). I'm one of the apparent few that actually like the "black rubber grips." As the one gent alluded to, about 75%--if not more--of all Colt SAA production from 1873 to present day has been the "black rubber grip" as stock equipment, and the two became synonymous. Ruger (originally in the 50s and now) was capitalizing on that history/connection--and cheaply as has also been said. Like cheap factory wheels on a new 4x4, they also know that a good percentage of owners are going to want to swap out to fancy wheels of their liking from the get-go anyway, so why bite into costs by doing it themselves with what *they* think individual folk will like? Factory wheels are nicer nowadays and fewer people are bothering the extra cost/hassle on their own, but you get the idea.
Btw, for those that don't mind the look, but don't cater to the feel--or just want to buy time tolerating them 'til your replacements come in, the Ruger "black rubbers" can be made to feel less plasticky/ more "rubber" (i.e., less cheap) with a few rigorous minutes of 000 wool over the sink. Take the grips off or do it on the gun. You'll want to mask off the already smooth border lines anyway, so I just do it on the gun (in the process, masking off metal as well of course). This takes the harsh points off the "checkering," but--depending on how far you go--still leaves them "new" looking but without the new plastic sheen. Have also done this on the USFA which suffers (but less) from the harsh sharpplasticitis. Take as much--up to "antiquing" them (00 as well maybe)--or little off as your objective is. In any event, you'll be surprised how much "rubber" dust comes off with just a few minutes...and they do look and feel a bit more "quality."
You might try these.
