Hmmm...a 45-degree angle? Not sure, but it's very possible with a Tec-Lok clip. I've been carrying the TOPS CUT 4.0 SOB for the past 7-8 months. My environment is different (Afghanistan), but I do dress "business casual" most of the week (of course with Body Armor and at times a battle belt which interfere with carry the knife in that location). While the positioning is more "scout" style, the poly-fiber loops on TOPS' sheath are simply awesome, very secure, easy to don/doff, and actually keep the bulk to a minimum.
I like that sheath so much, I'm going to have Red Hill Sheaths make up a couple more for some other knives when I get back home. If you're set on that angle (45), I would pick up a Tec-Lok and if your sheath isn't compatible, you can go the cheap route and drill a the holes, or get a custom sheath made, pancake-style is the simplest and cheapest. One issue with the Tec-Lok, is that if it's not a tight fit on your belt, it will slide. I like the dual poly-loops as I can strap them on both sides of my back-side belt loop, leaving the sheath extremely secure.
I've also seen knives angled 'down' at a 45 degree angle for faster access. If it rides high enough on your belt, it would stay pretty concealed under a jacket. The key is a very secure-fitting Kydex sheath.
ROCK6