Perfectionist,
The place that I bought my holster from is called
Sideguard Holsters.
In fact that exact holster in this photo is on their website (with the exact same gun in it).
The design of the holster is not that special, it is a standard IWB leather pancake type of holster. However, it is the materials used and the technique used to make it that allow it to perform well.
The leather is thick and stiff and provides retention but is still easy to draw. It also stays open (i.e. does not collapse when the gun is withdrawn), so re-holstering is easy. Yet, I can hold the holster, with the gun in it, upside down and shake it and the gun will not fall out. It is even more secure when it is in your waistband and your belt is cinched tight. It took about two weeks to break in but when worn with a
proper gun belt, you can sometimes forget you have it on (even with an all steel gun and thirteen rounds of ammo). Each holster is made individually and especially for that particular model of handgun. He has molds for most of the popular handguns but I doubt he would have one for an IOF. He might have one for a Webley though. He does have other types of tuckable holsters for revolvers that have only one snap or some with just a belt clip. I feel the snap is more secure than just a plain belt clip but other people might have different ideas. However, a single belt clip would be much easier to hide with a cell phone holster.
The snapped loops allow for easy on and off. I can have the gun/holster combination off in about ten seconds if I have to enter someplace where carry is not allowed. Pull shirt up, unsnap both snaps, remove gun and holster as one unit and store in secure location and then tuck the shirt back in. It takes longer to tuck the shirt back in that to do the rest of the maneuver. When I am outside the house and carrying, I keep the gun in the holster at all times. This prevents inadvertent or unnecessary trigger manipulation, thus lessening the chance of having a negligent discharge.
This type of holster is called a "double snap tuck" by the manufacturer. It means that there are two snapped loops and that they allow your shirt to be tucked in over the gun. The two leather pieces that the snaps are sewn onto, are only attached at the bottom. This allows the shirt to be tucked in behind that leather piece and the body of the holster, completely covering the gun. To draw, you reach over with the left hand, grasp the shirt material and pull it up. This exposes the gun and allows you to draw with the right hand. It also keeps your weak hand out of the way of the gun (and tucked in close to the body) when pulling it up and extending it. There have been people who have shot their own weak (non-dominant) hand when drawing in panic mode. The manufacturer is a small custom maker who does very high quality work. His lead times and prices are low for a custom holster. I have met him and he is also a very nice guy. he might do business with you, even though you are overseas. It might be worth an email to ask him. Another thing that I would like to mention is that his products are very durable. My oldest holsters from him were purchased in 2009 and they still look brand new.
This is where I get my gun belts from:
http://www.jbgunbelts.com/.
Jerry is a retired US navy guy and started this as a hobby but the demand for his belts increased to such a point that he had to start a business.
For a custom belt, his prices are low and his lead times are excellent.

This is what I mean by support. Can your belt do this?
That's a SIG 2022 with 15 rounds and two loaded 15 round magazines on the other side.
Check out the Tuck Clip and Tuck Snap on Sideguard Holster's IWB page. They might work for you.
“Never give in, never give in, never; never; never; never – in nothing, great or small, large or petty – never give in except to convictions of honor and good sense” — Winston Churchill, Oct 29, 1941