[Skribs]

My favorite video game of all time is Descent, mainly because I enjoyed the six degrees of freedom. You could control pitch, yaw, roll, move forward or backward or slide across the x and y axis. Well, I would like a OWB holster for my M&P that has zero degrees of freedom. Here's specifically what I'm wanting:

Designed for M&P 9C
OWB, doesn't hang way out there but not pressing into my side, either (so I can get a grip easy but its not sticking out)
Does not let the holster move on the belt at all
Retention strap (or some mechanism that doesn't let the gun move unless I tell it to)
Left-handed

In the past I'd been 100% kydex user, but now I'm thinking I'd be okay with leather provided it is black.

[TAKtical]

I could make a kydex holster for you, or a convertible with a kydex front and leather back.

[JTQ]

I can't think of any kydex holster with a thumb break.

For leather

Andrews Custom, try the Saddle Style

http://www.andrewsleather.com/traditional.htm

Davis Leather has a few models

http://davisleathercompany.com/concealedcarry/

Simply Rugged, Tribute

http://shop.simplyrugged.com/ecommerce/Tribute.cfm?item_id=158&parent=669

Most kydex holsters (leather holsters too), even without a retention strap, are very secure. You can hang upside down and the pistol is not coming out of the holster.

[allaroundhunter]

Safariland has some good offerings

http://www.opticsplanet.com/safariland-518-paddle-holster-plain-black-left-hand-518-291-62.html

And you might like this one more:

http://www.opticsplanet.com/safariland-6367-als-belt-slide-holster-stx-tactical-black-left-hand-6367-219-132.html

Here's a pic:

http://images2.opticsplanet.com/755-405-ffffff/opplanet-safariland-6367-als-belt-holster-slide-sample.jpg

[gunlaw]

Galco COP 3 slide. You can order one made for the M&P. About $80 delivered.

[9mmepiphany]

Given your requirements, I think you might find what you are looking for in one of the Safariland holsters.

I'm partial to the SLS or ALS equipped models...depend on if you want to move your thumb forward or rearward when releasing the retention