Couple of ideas.
The actual harness part can be bought from the various holster makers such as Galco, Bianchi and so on. That might be a good option.
As for the holster itself, see if you can rig up a temporary one out of thick canvas or something so you can try various angles to hang the knife from. You don't want to go through all of the work of making one to find it's uncomfortable. A major consideration is whether the knife will hang straight vertical, slight can (what I would think would be best for drawing) or even upside down, either straight or with a cant.
I've seen a couple of kydex rigs done for pig stickers that were slightly canted with the handle forward. Of course they were designed to be carried over clothing. Are you wanting this one to be concealed or open?
I've done a bit of leatherwork and designed and made a Huckleberry (think Doc Holliday) rig for a pistol once that was quite fun. Just e-mail and I don't mind to help you with any suggestions.
Charlie