Not perfect, but an excellent option to have on the market - Ridge Outdoors Gun Holster for Packin Tee Shirt

Honestly, unless you really have no other choice (and a lot of people don't), I wouldn't recommend "shirt carry", though I'll admit that was never how I intended to use this product.

Actually, I wanted this to sew to the inside of my motorcycle jacket for "motorcycle carry", hehe. And it worked beautifully. I'm left handed, and I wanted to cross-draw so I purchased the left-handed holster to sew to the inside of the right side of my jacket. It fits anything bigger than an LCP, being perfect for 1911s and S&W M&P Shields. We can debate whether carrying a pistol in a motorcycle jacket is safe or not, but if you're riding on two wheels your options were limited to begin with. Security wise, well, obviously it doesn't grip the pistol or protect the trigger as much as any kydex holster, but it's good enough. The best part probably is that if you're not wearing a pistol, the "holster" is unnoticeable and doesn't even look like a holster.

All in all, I'm glad this product is available. Might not be the right solution for a majority of people, but it sure does have it's uses.