On original Colt Single Action Army revolvers and through their newest versions - the hard-rubber grips were fitted to each and every gun.
Even though today's Colt uses plastic - that fact remains.
They're all slightly over-sized for that reason - to accomodate the various differences.
You can get replica grips from Gun Parts Co., Jack First, Brownell's and Dixie Gun Works - and I'm sure there are more suppliers.
Go to your search engine and type in 'replica Colt grips' - hard-rubber grips - or some variation on that theme.
You'll most likely find more vendors that you'd ever expect.
The outfit - 'Vintage Grips' - made 'actual' hard-rubber grips - but I'm not certain if they're still around.
Those were nice - as long as there weren't any bubbles from the casting process.
If you get a set of over-sized grips - sanding off the excess is easy - and you can smooth them with no problem - just go slow, and remember that on the originals - the fit of grip panel to backstrap was flawless, as those parts were buffed together.
And - since you already want to change the look of your piece - there are checkered faux 'Ivories' that will require the same amount of effort...
Good Luck.
Scouts Out!