I used this one for my Sig P320 fullsize 9mm at Front Sight Training. Very adjustable, and a paddle, slide or both (MOD) are available. Uses a thin springy piece of metal to apply pressure when holstered for good retention, and flexes when drawing or reholstering to allow the gun to glide smoothly in or out without having to muscle it.
Comes with replacement screws, plus a variety of spacer and screw lengths to adjust tension.
As you see if you watch the video, to use the same holster base for another gun, just order the shell for that gun and replace the original one. $12.88 plus shipping, and you have a holster that fits for multiple pistols.
I recommend once you get it adjusted to your liking, add some lock-tite to the screws. Mine came apart once from screws falling out. Good thing I had spares! That was probably around the 400-500 round mark.
Shipping took about a week, and I really liked using it. With no thumb levers, finger buttons or other retention mechanisms, it's perfect for a training holster or concealed carry. If, however, you intend to open carry, I'd recommend something like the SafariLand ALS line with better retention.
http://aliengearholsters.com/alien-gear-cloak-mod-owb-holster-outside-the-waistband.html