Biermaxx Co2 Pin Suits royal catering, klarstein, biermaxx machines.
Virtually impossible to source these days.
Bier Maxx beer dispenser (05581)
Item number: 45578309080 and many others.
I have these manufacturerd to order so please allow a few days.
Seals to suit are always in stock at https://www.ebay.co.uk/itm/353469522699