I Have Two Styles of K-Frame Holsters...
...for revolvers with three-inch barrels.
My three-inch SP101 fits into the DeSantis FBI-contract OWB holster (made for a S&W M-13/65) but has about half an inch of up-and-down slop under the thumb-break. It fits into the Kramer #2 IWB holster (made for a S&W M-66) but has about a quarter inch of slop rocking back and forth, due to the larger space to enclose the trigger guard. I can hold the Kramer holster, which lacks a thumb-break, upside down and the SP101 will stay in place but a slight jerk will let it fall free.
Personally, I would spend the money on a holster specifically made for the gun in question but, as my former teaching partner used to say, "It's your gunfight."