This is going to be a weird answer!
After researching, this is what I found. Rochester only produced one model at there factory in Rochester NY in 1948. (Your model)
Kessler ( Made up of ex-Crosman employees) bought out Rochester and made the same rifle but called it the Kessler (Two-piece stock model).
Kessler went out of business in 1950 and Numrich arms purchased Kessler. Numrich may still have some parts on sale.
However I suggest you also do a search on "Air gun repair" on the web and locate someone near you to have it repaired.
Also see the link below
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