Family member of mine wears this for carry while running.
Amazon.com: 5.11 Tactical S/S Holster Shirt: Sports & Outdoors
Amazon.com: 5.11 Tactical S/S Holster Shirt: Sports & Outdoors
Heed this warning. You want nothing rigid strapped to your body while riding. It's just asking for a serious injury. I know... I've got the titanium to prove it. A belly band type holster would be about the only on the body way I would carry on a bicycle. You carry on your hip, be ready for some really big orthopedic bills. Your chance of crashing and having bone damage from landing on your iron is a whole lot greater than being in a situation that requires you to draw.
Carrying on a bike is one of two things. Transporting it from one place to another, or for defense. If it's in your hydro pack or tail-bag, you're just transporting it. You'd never have time to get to it. For defensive situations, it needs to be accessible. A holster mounted to the frame, usually near the head tube, is the best option. Mechanical retention is a must here as well.