Welcome to the Forum
You are correct, X-frame revolvers share the same grip frame dimension as the K and L frame revolvers.
So if there is an existing K/L grip that you already like, just purchase another one or your X-frame
The grips that Smith and Wesson ships on the BIG Magnums were o-designed between Smith and Wesson and our good friends at Hogue. The rubber that sits between your and and the back strap of the revolver is specifically engineered to absorb recoil. The remainder of the grips is composed of a different so that you have less slippage
Up until a month or so ago, these grips were a Smith and Wesson exclusive offering.
Hogue has recently begun selling them also.
However if you want any of the special colors that were produced for the
Factory, you will need to contact Smith and Wesson. or keep your eyes open on the various auction sites
Black, OD Green, Yellow & Orange
I also have BIG hands and did not find the factory grip to be comfortable. I had always ordered my Hogue wood grips with no finger grooves. My contact at Hogue informed me that the finger grooves could be easily removed with a Dremel and the sanding drum
I left the top groove on since it is spaced good for me and removed the second ridge.