The best results will always come with a holster formed specifically for the intended handgun. That said, I will add the following:

1. A K-frame revolver will readily fit into a holster made for the L-frames. The fit will be somewhat loose, so the need for some form of retention device (thumb-break, etc) should be considered.

2. Being somewhat loose the K-frame revolver will always be moving around somewhat inside the holster as your body moves. This can be expected to result in holster wear to the revolver's finish over time, so you might want to consider a good soft leather lining.

Back in the very early 1980's when S&W first introduced the L-frame revolvers there were very few holsters available for them. Many people carried their L-frames in N-frame holsters, and many found that they fit nicely into Colt Python holsters. These were not the ideal solutions, but they worked for a lot of folks for years.