Making your own can be a pretty simple process, if you are moderately handy. Just looking at some should give you some good ideas; haven't looked at any how-to's but I'll bet there's some on this site.
As far as having one made, I recently received one I ordered from Steve Catts, "Leathersmith" - not a sponsor on this site, but well recommended. Good guy, very reasonable, and very nice work. Might take a while, but worth it. He very well may have a simple "pouch" style sheath in stock that would work for you. I got a pretty basic pouch sheath for my knife, but wanted it hand laced, rather than stitched, and also in a cross-draw style: first time trying one of those, and I think it's GREAT!
Just some thoughts for you.