Ohio Cycle advertises itself as 1959-1969 only, although some of the parts numbers do carry over. It's a real good source. although a bit crazy to deal with as they don't do on-line ordering (they have an on-line catalog), order have to be written and mailed, and payment is money order (no personal checks or credit cards). Nothing like 1969 mail order rules. ;D
Next step is to do a Google search under "vintage Honda motorcycle parts" - that'll bring up a number of places who deal in the stuff. And outfit called Western Hills Honda in southern Ohio has done me good stuff in the past.
By the way, I'm not sure how conversant you are on Honda part numbers, but the critical part is to get the xxxxx-xxx- (first two number groups) matching. The first is the part definition (first two digits are the function, the remaining three are the component). The second group is the product code. Every unit that Honda has designed has a product code. Totally numerical ones are old, currently they're either alphabetic or alphanumeric (for example, a Metropolitan scooter is GET, one model of lawn mower is ZL8). Yes, I'd love to know what 001 is. Most likely a 1949 Dream.
The third group in the part number is the classification, and it changes with every revision to the part. Among other reasons, most of which I'm not privy to. Say for example, you're looking for that right sidecover gasket (11394-302-306) and you find a 11394-302-000. That's the same part, just an earlier version - it'll work just fine.
To further confuse the issue, if that last group is a five digit alphanumeric (say, 000ZA) that means it's a painted part, and the two letters on the end delineate the color.
Confused? It's actually very rigid and organized. About the only bit that doesn't work like you'd expect is that final classification group doesn't go up in one digit increments (000, 001, 002, etc.) I have no idea what governs the change, I just know that the higher number in classification, the newer the part.