This is another that might work for caping. It has a finger stop, and enough handle to hold on to.
I was at a taxidermist shop one day and he was caping out a bear. He had an entire case of single edge razor blades nearby, and he seemed to be doing okay. He wasn't using a holder for the razor blade. That is why I thought thin and sharp would be what you needed.
Or a scaled down version of this: