This is what I found while searching for RB to SB grips
Of course, the original OEM S&W style. These can be found on eBay and other gun related auction sites. Even NOS. They fit the round butt stlye J frames. There is some dispute whether they will fit SB J frames.
Then there is the New OEM S&W conversion grip. These can be ordered direct from S&W although most of the time they're backordered. When you can get 'em they're very economical. I've been told they only fit RB J frames. Photo courtesy of someone here on the forum. Forgive me for forgetting your name.
There is the Kelly J frame conversion grip. They only fit RB. They can be found at kellyarms.com. Any combo of the 3 colors, checkering and medallions are available.
These I found on eBay. Italian made, sold by a US vendor, leather inserts. I have no other details except they fit RB. Interesting looking.
Then there are the 2 following conversion grips by the same eBay seller and ship from Thailand. The seller claims they fit RB & SB.
Lastly, there is the almost ubiquitous Sile conversion grip that can be found nearly anywhere on the web.
Post your photos, especially if you have a different conversion grip.