This eBay link however indicates that our OEM cap was also used on other bikes so this may be a better alternative source - if this is in fact, the case.
"CNC Gas Fuel Cap Tank For KAWASAKI KZ400H1 KZ440A1/A2/A3/A4 KZ440D1-D6/G1 KZ550D"
amendment: seems the above listing is typical EBay seller hype. Not to mention the rather laughable is the "CNC" notation !
1980 KZ 1300 sr# KZT30A-009997
Always High - Know Fear !
Neither one of those have the lock assembly though. Mine is destroyed, but the actual cap is okayish.
I really just need a complete, good used cap. Tried the alternate application as suggested, but I ordered a $5 cap for one of those bikes (don't recall which) and the cap is shorter, and the lock cylinder doesn't interchange.
Here's a listing for a KZ440 cap that looks shorter and doesn't have the vent. I believe one similar to this is what I bought and couldn't make work.