Last year at Blade Show West we took our F1 in hopes of finding an inexpensive leather sheath
(this was before I met some decent custom makers).
and this is what we found;

it cost only 5 bucks (for leather!) but we found out many
(if not all) of our other small blades fit in it pretty nicely;

we put a cardboard sleeve in for the smaller blades or else
they go too deep.
All these blades fit in snugly (some alittle more than others),
but none will fall out (why I like pouch style sheaths).
I'm surprised I don't see/hear more about "universal" sheaths, but
hear all the time about custom jobbers.

I think I'll ask my friend to make a couple up so I can use them for many of
my blades, maybe with a loop for firesteel or a pouch for a SAK.
because I can't afford a custom sheath for each and every blade now
(even though he's darn inexpensive).