Jim, Welcome !
Please send me an email with your vins, we will get you registered to be member #128 ! sandcast232@yahoo.com
As for parts, i would first suggest, especially for the part you mention, try your local Honda dealer first. Having a part number to give the dealer is always a good thing. You would be surprised what is still available from Honda !
The other good vendors are Western Hills Honda in Ohio, Yamiya750 of Japan, David Silver Spares of England and Classic Motorcycle Supply of the Netherlands. Within reason, you should be able to obtain any part you need to keep your bike roadworthy.
Where are you in Iowa, anywhere close to Sioux City ? That's 50 miles from where i grew up, we bought our CB750 new from Olson Brothers, Sept.69.