Very cool engine!
Are you sure you want to bring a fuel pressure line into the cab for a gauge? I like old school, but some things are better left in the past.
I would say what you have is a boost compensating, non adjustable, blocking fuel pressure regulator with integral sediment bowl filter.
There must be a spring that presets the pressure and the top portion you could not split adds pressure when the boost comes on. Any diaphragm with similar dimensions should work, but I'd be hesitant to mix and match given the need to balance fuel pressure with boost pressure.
I don't think you will find a replacement all in one unit with modern materials. The glass bowl portion is not something manufacturers would see much demand for the last 30 years since EFI took over the hot rod market.
It would be easy to find it as two pieces: a modern boost compensating, adjustable, blocking regulator and a separate sediment bowl/filter (or modern disposable filter).
You can get the regulator portion with a built in gauge, a threaded port for a gauge/sender or just put a T in the line between regulator and carb.
There are also electric fuel gauges with 0-15 PSI range that probably covers what you need, and no fuel line needed in cab.
some examples i have no first hand experience with:
https://www.fuelab.com/55501-fuel-pr...-regulator/p43 (you should be able to use threaded vent to connect to boost pressure but ask be fore you buy)
https://www.speedwaymotors.com/Glass...l?sku=91011778
https://www.aircraftspruce.ca/catalo...s/10-25058.php