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For IWB carry with my Glocks, I use several older Blade-Tech holsters (not sure of the model, or if that model is still made), and a Vanguard 2 from Raven Concealment Systems.
Not sure what you meant by "not concealable", but many folks have trouble with the grip pushing out to the rear on their clothes when they carry a larger pistol. With any large-gripped handgun, to assist with concealment, many experienced shooters/instructors recommend angling the butt forward and the muzzle to the rear. If your handgun is pointed straight down at the ground when holstered, the butt sticks-out to the rear the maximum amount, and tends to "print" on your cover garment; with it angled so the base of the grip is almost directly above the end of the slide, you will minimize this rearward projection. It takes a bit of practice to get used to this angle, but it is worth the increase in concealment, in my opinion.
Here is a link to an online concealment holster article that you may find helpful:
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)