Thought I could help but it doesn't look good....
Went through my receipts. In 2004 I bought one from NAPA, p/n 703-1113 which seems to be changed or discontinued. Rubber seal in it failed in 2018 and I found one at Oreilly's, p/n STA 10491 which unfortunately now shows a black plastic cap.
So this post is pretty much worthless -- unless you can use the info to track down what you want. Oh BTW the neck on my K20 is 2 1/4" dia.
EDIT: Found one (STA 10491) on EBay but it's out of stock.... Got a picture though if that's the type you're looking for.
https://www.ebay.com/itm/Locking-Fue...-/184489405258