Corny Keg PRV

[Cobnut]

I pressed my 3rd Corny keg into action over the weekend and uncovered a problem: a leaking PRV.

All the kegs were bought 2nd hand from a local older gentleman and I can now see that they are also getting on in years.

This keg has a lid with a built-in (metal) PRV, so no option to change the PRV (unless they can be drilled out which doesn't seem worthwhile).

Fortunately, I was able to get a seal by applying a "dollop" of petroleum jelly to the underside whilst holding the PRV open. I'm hopeful that this will hold for the duration of this beer, but do feel the need to resolve it properly.

So any suggestions as to best source for a replacement lid? Doubtless there are cheap-and-cheerful options as well as pricey-and-poor, and many others, so seeking the advice of the ever-wise JBK!

Thanks in advance.

Cobnut