SB or RB? If it's SB, you need Pachmayr Presentation Small grips (SN-S). I'm pretty sure that these are not made anymore, but they are around, and not expensive. Other than that, I believe that you will have to go custom. Over here, Herrett's. On your side of the pond, maybe Nill?
If you have a RB N, maybe Hogues that take advantage of the RB, NOT "conversion" (RB-SB) grips. Again, possibly Pachmayrs, or maybe even RB service grips (Altamont?) and a Tyler. There are probably other ready-made RB grips that would serve, but I don't know for sure what would be best for you.
What are you shooting? It is hard to imagine anyone using an N-frame revolver in what we call bullseye competition, other than possibly a 25-2.