Below I provide some links I find useful, maybe you will too
Dennis Carpenter Follow his 1937-65 Cushman Parts link. He appears to have Tillotson carburetor and Wico magneto parts though I've never used this resource
Jim's Antique Air Cooled Engine Parts I haven't used this resource yet but he states he has Lauson/Tecumseh parts
Discount Marine Parts Haven't used these folks but they list Tillotson Caburetor Parts and rebuild kits.