I live in Arizona. I tend to use a fanny pack most of the time. With shorts and T-shirts it is very hard to conceal otherwise. My MK-9 will fit in the smallest of fanny packs.
I own an MK-9 Elite 98 and a K-40 in matte stainless steel. The K-40 broke in in about 300 rounds. The MK-9 took much longer. I have now shot over 1200 rounds through the MK-9 and have had no malfunctions in the last 300-plus rounds. I think the gun tolerances are so tight that it takes awhile for things to seat.
If you get a gun in the MK series, I would stick with the 9mm. It's my own opinion that unless you are a very large man, that size gun in .40 caliber is difficult to control.
If you are going to get an MK-9 gun, I would strongly urge you to spend the extra money for the night sights, as I think this is an advantage over the J-frame revolver you are currently carrying.
I have found Kahr guns to be extremely accurate, even with the small barrel on the MK-9.
If you're interested in leather holster for other times of carry, I have one of the Alessi holsters (I have several of these for other guns as well). They're good quality and gun access is easy, with a tight fit. The magazine holders from Alessi fit the 9mm well. I found the .40 cal magazines were very tight and needed significant breaking-in time.
Happy Memorial Day!!