This is not a solution for the RTV problem but an idea how to make a multiple mold.
You may have seen a letter being sealed with wax and a stamp pressed into it.
I was thinking maybe you could make your part into a stamp and press it into a sheet
of wax multiple times to form a molds. Then pour and squegee the molding material
into the depressions. Some one on these forums made deck boards in a similar manner.
I don't think they used wax though.
Another idea is to make a punch out of your part and press it through something like the
sides of soda bottles. The material would be cheap and won't tarnish.