I was recently shopping for a heavy duty custom KYDEX knife sheath
and the issue I found was that if your knife of choice is not extremely popular,
your either forced to make your own or to send your knife to a custom sheath maker,
by the time you pay shipping both ways and buy the supplies and pay to have it made, youll most likely be close to $80-$90 for a one-off original, and you'll be risking your knife is lost in shipping , or the guy making the sheath may not get it done exactly how you want it,
then you look at the cost of the tools and materials and its obvious that you could set up yourself with the minimum required tools and equipment for about $200-$300 and make yourself several.
obviously, if you want more than the minimum tools it might cost more but you also have many options.
now to me , a guy that owns several knives and a few handguns...
that sounds like owning the required tools is almost mandatory
while I really like the idea and design, options,
available with a properly designed shoulder rig,
(obviously check local concealed carry laws as some states allow handguns but not blades to be carried as defensive weaponry)
use of a blade shoulder holster ,in a few cases,
makes a great deal of sense,
as its very difficult to carry a longer blade,
in a traditional belt holster sheath, extending down along your hip/leg, or horizontally behind your back,
and still draw it if seated, or during operating a vehicle,
and convenience of having a larger blade in a shoulder holster,
I doubt its worth the asking price, in the commercially available designs ,
from many sources,
simply because anyone with a bit of fabrication skills,
and a few inexpensive straps, buckles and some leather and kydex,
almost anyone, could with some practice and taking the time & required thought, experimentation, and testing your options many people might
duplicate or even improve on the design,
especially once you grasp the fact the knife sheath is not
included, in the linked shoulder rig linked here,
you'll need to adapt the one you have or purchase to fit , correctly,
and function with the shoulder holster straps supplied
and many handgun shoulder holster rigs ,
quality suspenders and commercial belts,
can also be reasonably easy to modify,
to hold a blade/sheath on the other side,
of that commercially available shoulder holster,
to counter balance the handguns weight,
and most people I know also prefer at least a dual or triple magazine,
hip belt mounted rig as having magazines on the shoulder rig tends,
to make them harder to consistently access and limits easy concealment,
as having many spare magazines, hanging under your arm,
add considerable thickness, under concealed clothing,
in an area harder to conceal easily.