Go to https://www.aomci.org
Once there go to the "webvertise" section and put an ad in there for the parts needed.
Use your model number followed by the year and horsepower and use "super Quiet" as well.
"I purchased an RDS-21 1959 35hp Super Quiet and am in need of a ..................
Make sure you put your physical locaton in the header for the ad.
Those are nice engines!
Make sure you check the gearcase seals after the first few runs, change out the gear oil first.
Change out the impeller or the complete pump depending on condition of the pump housing.
Check, clean, set the points and verify operation of the ignition.
Probably would benefit from a good OEM carb kit as well.
Always run the engine at the manufacturers recommendations for fuel oil ratio. Do not change it because of today's oils.