The 'stitch finger' is, I trust, what is sometimes called a 'presser foot'? If so, it's a fairly complex part,
with a fitting to mate with a manufacturer's plunger end (often thumbscrew clamped). After making
it from (apparently) steel, there's a long tumbling (all surfaces to be smooth), and nickel-plating, possibly
rather heavy plating.
One example here is obviously a stamping from sheet metal, to which a hinge has been brazed; another
might be a coining, sculpted on the upper face. The feet are pressed into curved shapes.
There are joints, and one has an adjustable lateral offset (multiple parts with a thumbscrew)..
In a hobby setting, yes, these could be hand-carved. For small batches, it might be possible to
use a drafting program to make a 3-d model that could be carved in wax, and lost-wax cast, with some
hand finishing, in CuNi alloy. The only easy way to get replicas would be to make 'em in a 3d printer, with
(probably not very strong) plastics.
Sheet metal fabrication in mass production works, but would be uneconomic in one-offs.
It's a do-abe project, but not easy (many steps, many different tools required). The small scale
is similar to jewelry work, but it's in STEEL, not as easy to work with as copper or silver. And,
unless there's a model handy to work from, it's a BIG project to describe the shapes and dimensions
in order to specify a replica.
Have you looked at (for instance) Sears/Kenmore parts department? Maybe adapting an available
foot for another machine would be feasible.