[sc_rufctr]

What about a polymer like two pack epoxy with glass fibre reinforcing?

Have you ever seen or heard of "kitty hair"? It's very fine fibre glass hairs that's also mixed with epoxy and it's used to make prototypes by hand.
It's very strong when cured but you could make a simple alloy insert for the blade to make it even stronger.

You could make a two or three piece mold with a proper molding polymer backed with fibreglass for strength.
After mixing and filling with epoxy and glass fibre you bolt the mold pieces together. Sounds messy because it is but the results can be very good.