Extended run gas cap for Champion Digital Hybrid 4000?

Nobody makes a correct replacement cap that I'm aware of
How ever SuperGen used to sell a kit for champion generators, came with a vacuum operate pump,, connecting hoses, nipple etc,
A diy install, I put one on a 3500
CAT5 inverter generator, worked fine as long as both were on the same level ground, my champ was on a sliding compartment tray/drawer so I would put the extension tank/can on a snack table or chair next to the genny, sorry don't have a link, using my phone not my laptop

Be careful online, I ordered one for my 3500/4000 and when itm arrived it was the wrong cap, one with female instead of male screw thread for the cap. The seller never replied to queries so I'm stuck with it. It was well made tho, milled aluminum but worthless.

It is just a gravity feed system with a tube into the cap from the gas tank. Which is a outboard fuel tank. The vent on the gen is plugged and the gas tank needs an open vent. If you want to drill and tap the cap on your gen you could probably put it together fot $10 or $20. Not much open space on my cap anyway. I don't see any obvious way to drill the top of the tank unless you braze or maybe jbweld a fitting on top of the hole. No inside access.