So, small update, it's not really possible. Maybe with a 3d printer and some time to get the dimensions right. you have around 3mm of space where you need to fit liner and glue, anything more and the blade will lock up inside the scabbard at around 4mm of material. So you would need to print a full liner. I will post some findings, maybe someone will find this helpful.
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The Windlass side liners are either HD-PE or PET/g, can't tell for sure. They are 0,54mm thick and pretty roughly cut, meaning they are a bit different, like 2mm more here, 2mm less there. They look to have a similar shape to the blade, not the scabbard. Beginning at 4cm, widening to 5cm and coming to a point while the scabbard is more or less 5cm wide all the way.
Plastic choice:
PVC is problematic when it gets hot, it outgasses chlorine, forming HCl with moisture, very bad for metal, but also makes molding it a bit unhealthy without PPE
PLA is an unknown, it could still have lactic acid or it could not, so a gamble to 3D print with it
Kydex would be good - low molding temp of 80°C and very soft on edges, but I can't get big enough sheets, or any sheety for that matter around my parts
ABS is more or less like Kydex, but needs a more temperatuer, at least 110°C, and isn't as oil resistant, it's also hard and brittle
Acrylic (PMMA) is also an option, again high temps needed, over 150°C
Polystyrol isn't that oil resistant, so I wouldn't
My choice was PETG, bending temp is slightly above 100°C and I have made liners for knives from PET and it worked pretty well, but we will see. With the right 3D printer you can get it as filament as well.
*I tried to bend the PETg and it worked well, begins to bend at 60ish°C, but it's a space problem. Bending it you can't get it to perfect shape and thus have even less wiggle room.
Scabbard is slightly over 1mm thick, between 1,05-1,15mm.
53,2mm wide@throat
52mm 1cm in
51,8mm @ first band and stays that wide for around 2/3 the way to the next band when it begins to taper to
50,3mm @ second band for again 2/3rd of the way down, then it tapers to
48,2mm before the flared parts of the tip.
It's flat and 14mm on the inside top at the throat and 11-12mm at the end. the lower portion is a rounded and about 5mm wide
And now for plan 324: I'll do a full wood one.