This item called the Drive Pin; it is included in all of our propeller replacement kits along with the propeller and all needed tools and pieces needed to install a replacement propeller. Please do not confuse this with a Shear Pin that is designed to break when too much force is applied to the prop. Our prop doesn't utilize this Shear Pin mechanism.
You can find the prop kits here: https://newportvessels.com/trolling-motor-accessories/.
Or you can order the drive-pin with a washer from our Parts page.
(Please note that the 'Small' props are compatible with 36lb-46lb thrust motors, while the standard props are for 55lb-86lb motors.)
If you need a replacement pin immediately, you can source a generic steel cylinder to act as this pin piece at your local hardware store using the measurements of 1" length x 1/8" diameter for the 55lb, 62lb, and 86lb motors; and 1" length x 1/16" diameter for the 36lb, 40lb, and 46lb motors. You can specifically ask for a "Drive-Pin-type" component and the retailer maybe able to better direct you to the correct item.