I have one of those. It uses the same prop as my 1958 10HP Evinrude.
The Solas 2011-83-08P is supposed to fit. They can be found on eBay, Amazon, and here on iBoats for less than $100.
The pin is part #0307949, and the prop nut is part #0305394. They also can be found on Amazon and eBay. The cotter key is nothing special - get one that fits at any hardware store.
FWIW, there is a used prop, pin, nut, and cotter key for sale at the moment on eBay. The trouble with used props, especially those that are 60 years old or more, is the rubber bushing inside may have been spun or has deteriorated until it is ready to spin. This can happen without the seller knowing it. So, they are a gamble.
Good luck.