I've read some old threads about replacing the air pressure system on this forum. I think they're from many years ago. Just start searching and you'll find them.
However, I would encourage you to consider sticking with the air pressure system. I know some folks here will disagree with me, but in my opinion they are far superior to the modern systems. The water pressure at my house is about 45 psi. So I hook a hose up to the camper, with all faucets closed, and it fills the tank to 45 psi and stops. I've got a small 12-volt air compressor hard wired into the camper. Every three or four days, I just turn it on for a couple of minutes to keep the pressure up. Other than that, it operates exactly like my water system at home, and it's absolutely quiet, unlike the electric pumps, and no priming. I carry a old style bike air pump that I could pressurize the system without the battery if I needed to, but I've never used it. Winterizing is very simple. I just empty the tank, and fill it with compressed air. Then I just have to open faucets one at a time and it's done. I did re-plumb the entire system with pex.
The disadvantages are; apparently the tanks corrode from the inside and can leak. Replacements are hard to find. I ran an inspection camera inside mine and saw no corrosion. They don't hold as much water as modern plastic tanks. Since they are cylinders, they waste space. I think mine is about 20 gallons, and there has to be space left in it for air to compress. That has always been plenty of water for me and the wife. We just plan out where we can fill up, and carry a couple of collapsible water jugs to supplement. I know that this would not be enough for some families.