I have made several stubbies out of cut down regular ratchets (Kobalt danaher round handle, and gearwrench roto head) and I did make a set of 3 (one in each drive size) palm ratchets out of the harbor freight roto heads by removing the roto head from the handle and then clipping the pictured piece of PVC pipe (shown below) around the roto head (with the posts through the holes) for grip. I only have pics of the PVC piece by itself because I ended up eventually putting the roto heads back together and using them with just a cheap custom extra-light handle instead so they swing around a lot faster and have a better weight balance for my tastes vs. stock. Now they get a lot more use. They worked great as finger ratchets, but I just didn't use them as much as I thought I would.
I have thought about just cutting the handle off of a regular round head ratchet and then taking a thin grinding wheel and scoring the outside edge lightly for better finger grip, but I haven't tried it yet.