You should be able to run any sensor with a standalone ecu. Just calibrate it to suit.

Although there are loads of Chinese shit out there. A Genuine GM 3 bar is hard to beat, but most are chinese now.

Should be plenty of Bosch 3.5 or 4 bar sensors knocking about from the diesel world, although some dont go particularly low in the vacuum range.

Or you can go expensive like branded stuff from KA Sensors etc

Or VEMS sell some decent ones at not too bad money