Thanks, that helps, better than the stack of old misc. washers I was trying to use. I found a similar spacer on Amazon and Fastenal. Just look for '5/8" Shaft Collar' in your search engine and look for an inside diameter of 5/8", I figure stainless or carbon steel would be the best. The shaft did measure at exactly .625 with my digital calipers. It looks like the 1/2" wide ones will work. I will report back when I get them in.

Climax Metal C-062-S Shaft Collar, One Piece, Set Screw Style, Stainless Steel, 5/8" Bore, 1-1/8" OD, 1/2" Width, With 5/16-18 Set Screw: Amazon.com: Industrial & Scientific

Paul