Not too many knives work well in that "scout carry" position. You need something much flatter. Best I've used for that particular location (I had body armor on, so it was less of an issued when seated), are the TOPS CUT 4 and the ESEE 3 (right around your price range):
The stock TOPS sheath is actually pretty decent, but the Armatus sheaths are top tier. Even without body armor, they were tolerable to wear when seated, but they are noticeable when you're in and out of seated transportation modes.
One recommendation instead of the small-of-back scout carry, is in the front, horizontally. I'm right handed for shooting, so I carry them horizontally at my 1100 position. I can draw it with my strong-hand for a conventional/utilitarian need, or I can draw it with my weak-hand in an icepick grip: my primary defensive training style.
The challenge isn't access. The SOB-scout location is pretty easy to access, but it limits access to just one-hand and it's a PITA to re-sheath. If you're planning on using the fixed blade as a utility knife, the front-horizontal method is much easier to access (both hands), and much easier (and safer) to re-sheath if you're using it often.
ROCK6