I agree with onetuza's options of the SmartCarry or a shoulder holster. Since you seem to be leaning toward the shoulder holster, let me give a review of a couple I own, plus one I don't own:
The deep concealment shoulder holster
Deep Concealment Shoulder Holster is quite functional, but I need to wear a t-shirt underneath it for comfort because the material is not comfortable next to skin. Maybe that's not an issue for you. One downside with my deep concealment shoulder holster is that the 13-round mags for my XD-45 won't stay in the mag holders. They are too top-heavy. When I bend over, the mag ends up in my sleeve. This holster is quick to put on and quick to adjust.
The kangaroo shoulder holster
https://deepconceal.com/ is a more basic one. I've heard it can be worn directly on skin since it's made of cotton. I don't own one, but I like the idea of wearing one without a t-shirt in warmer weather. Unfortunately, the site only mentions using the holster for small and medium-sized guns.
The truss holster
SpecGear TRUSS Holster Tactical Belly Band Undercover Weapon System Pictures and Features for Law Enforcement is a deep concealment holster on steroids. The truss crossdraw has an opposite cant when compared with the deep concealment holster, so one can hide a firearm with a larger grip than can be hid with the deep concealment. The truss I purchased has places for 4 mags vs. 2 with the deep concealment, and has velcro staps to hold the mags in place. My truss also has 2 cuff-size pockets and one flashlight or knife pocket. The truss is wider and heavier built since it has more pockets for stuff. It comes in a strongside draw or a crossdraw. (There are a few different configurations based on draw side and size, so not all have the exact same number of compartments.)
A possible downside to the truss in your environment is that it is thicker than the deep concealment. An accidental brush from someone might cause them to wonder what they bumped. The truss has 2 rows of velcro sewn on the outside, plus it is double thickness compared to the deep concealment single thickness.
Both have their place. The deep concealment is quicker to adjust since it fastens with velcro, although once I got my truss set up, I've never had to adjust it. Yes, the truss costs more.
If anyone bumps your shoulder holster or feels the strap across your back, you can tell them you like to wear your back brace in order to stay healthy. :image035:
As someone mentioned, thin guns are easier to conceal, but larger, thicker, and stiffer shirts also help conceal.
Good luck.