The prop is a 9" X 9 1/2" 3-blade for all 1-30 models from 1950 through 1953 according to the 1956 Scott Atwater service manual, chapter titled: Section J – Outboard Motor Specifications. Also, Michigan sold props for these motors in 2-blade & 3-blade with the 2-blade props designated for light to medium weight boats. Early stock 509 props used 6 rubber tubing strips in the prop for ‘cushioning’ the shear pin. These can slip at speed and should be replaced with 6 round solid rubber pieces.

I would try McMaster-Carr. Their catalog is over 2000 pages of industrial supplies (that is where I buy brass wire cloth (screen) for fuel filters in mesh size 100 X 100 which means each square inch has 10000 holes).
For example, they have super hard rubber rods in 1/8" to 2" dia, in 36" lengths plus many other different materials (nylon, delrin, etc).