You can try posting a free Webvertise WTB (want to buy) ad at the AOMCI (Anitque Outboard Motor Club Inc) website. A lot members have spare parts, motors, and parts motors. Salvage yards often troll through the ads for prospective buys.
Here is the link to AOMCI Webvertise. Please read the 1st link for the rules and 2nd link is the link for the actual posting.
https://www.aomci.org/cgi-bin/yabb2/YaBB.pl?num=1326461963
https://www.aomci.org/cgi-bin/yabb2/YaBB.pl?board=Webvertize
Here is a bunch of links to online salvage yards around the United States.
https://www.sea-way.com
https://www.outboard-parts.com
https://www.laingsoutboards.com
https://www.tcoutboard.com
https://www.fairwindsmarina.com
https://www.salvagemarine.com
https://www.marinepartsoutlet.com
https://www.outboardexchange.com
https://www.Superior Marine (800-338-9281)
https://www.budgetboats.net
https://www.americanoutboard.com
https://www.piratemarinesalvage.com
https://www.trixieslanding.com
https://www.mmmarinesalvage.com
Good luck!!