Holsters that work properly with the squared trigger guard can be difficult to locate. I like the Don Hume Double Nine (H721-5M) holster for my 3904/6 - should work fine with the SSV.
5903SSV owner here. Pretty much any holster designed for a square trigger 6906/6904 will work. Really the only difference is the grip of the 5903SSV is longer for the 15rd mag.