I have a suggestion, though it's not a custom grip. You might want to try PGS Hideout grips. They're available for K-frame round butts from Brownells. I also have smallish hands and the PGS grips work very well for me. The best part is they're only $18-19 so if they don't work well for you it's not a huge loss. They have a smooth model and a textured model.
Of the grips I've tried, the only grips I like more than the PGS are Ahrends boot grips without the finger grooves. The Ahrends grips are hand filling but they fit my hands well.
I haven't tried them for K-frames (but I plan to someday) but I also like Spegel boot grips. They're pretty slim but with a palm swell so they fill the hands without being overly large. Normally I'd suggest avoiding finger grooves for people with smallish hands as most of the time those grooves spread the fingers too far apart to get a solid hold on them, but the grooves on the Spegel grips are subtle and don't get in my way.
Of course, you can also try using a grip adapter. A Tyler T-Grip adapter and magna stocks work well for me, though I prefer a solid grip that fills in under the trigger guard. I haven't tried the BK grip adapter (yet) but I've read nothing but good things about them.
