noglider: not!
Scanners are cool and would be great for the external shape. The mold has four parts, it think, based on the hoods I have. Upper, lower, internal and one for the cable hole.

A short cut would be to have the interanl and cable hole as one part. The hood would be removed just like taking it off of the brake lever base. Still need the upper and lower. You can tell by the mold break line that follows from the front lower edge of the hood above the lever to the back.

Typically, soft tooling would be OK for low volumn. Make a negitive of the original part (cast it). Make a positive from the negitive. Create the soft tooling molds from the positive. This allows for a master to be used for creating replacement negitives.

What is not often mentioned is the shrinkage factor. Typically material shrinks after it cools. The percentage of shrinkage is related to the thickness of the material as well as the geometry. This is the trade secret value added in the process of creating the molds. Different materials have different shrink factors and often molds are "tweaked" until the correct result is obtained.

So as simple as it looks, it is not.