Keg Connection has some. At least one of them has a lock nut that goes inside the keg against the lid. I bought one thinking the size was smaller than it actually is.
new lid at that point.....ball lock pin lock, are interchangeable as far as i've notice, baught a new ball lock lid for my pin lock keg, no co2 leaks...and yeah i tried finding a PRV for it first, but a lid was only like $15.....came with a new oring!