I seldom mention this, but just this once, and don't ever ask me about my business again...Fist holsters, see 'Related Links' above...has the Ruger P89 on their gun list, so the holster is fit (boned) specifically for the make/model you order...it will be a perfect fit.
I have a half a dozen or so of the Fist #41 IWB/SOB holster with a clip...sits over my kidney not my spine.
It's 'palm out' draw keeps the muzzle away from the body during presentation.
It has become my favorite holster...the draw is as effective as strong side with some practice.
I know some who like it and some who don't...it's what works for YOU.
Stay armed...with Fist holsters...stay safe!