coutellerie -- welcome to the forums. One person, whose name is well known here, who truly agrees with you is Gary Graley. Gary makes super leather sheaths for folders. A good percentage of his sheaths are horizontal belt affairs. The clip must be removed for most or all his sheaths, for the tight fit necessary for continued carry.
Gary has quite a few knives. If he has the model you want a sheath for, then you don't have to send him your knife. If he doesn't own the knife, then you must send your knife to him so he can mold the sheath around the knife.
Chris Reeve Knives sells a leather pouch/sheath for Sebenzas. I believe they cost about $35. There are other, very fine sheath makers who would happily make a custom sheath for you.
I carry one of my knives in a sheath, not counting my neck knives. Otherwise, I'm pretty sold on pocket clips. But, part of that I'm sure, is that I don't work, so wear jeans or cutoff jeans virtually every day of the year. Don't have to worry about wearing slacks.
If you haven't noticed it yet, there is a search function that is now quite quick. You can check specific forums, or all active forums, or check several archived forums. I'm sure you can find Gary Graley with a search on this forum, and probably other sheath makers as well.
