Two pipe is a description that is somewhat open to interpretation. If two pipe means one inlet and one discharge port as used up to 1971 then exact reproductions are no longer available. If you mean two inlet ports with the bottom discharge port as used the 1972 and later cars mounted in the middle of the fuel rail, it 'may' be available. A touch expensive.
https://www.cvi-automotive.se/en/art...r-late-1800140
Unfortunately it appears to be out of stock; but, if you search the part number 243129 you may find that a local Volvo shop sells it - at an even more egregious price.
The two inlet port regulator should substitute for the early single inlet port regulator just fine if you cap off one of the inlet ports with a suitable rubber pressure cap. 243129 appears to be a later part number equipped with threads around the bottom discharge port. I expect that the threads were added so that it could be used in the early bracket or just kind of hung from the middle of the fuel rail as in the later cars.
If you don't feel the need to have an exact reproduction you should be able to use just about any adjustable fuel pressure regulator that will work with a base fuel pressure of 30 psi. You should be able source one from any supplier of tuner parts for Asian cars. These regulators will have a port to connect the intake manifold to provide a pressure reference signal. Just leave this port vented to atmosphere for use on the D jet system.
When I was looking around earlier, I did find a particularly nice adjustable atmospheric referenced fuel pressure regulator from Delphi. It almost looks exactly like the original Bosch FPR and has the correct 8 mm hose barbs so no messing around with fittings. Its Delphi FP 10545.
https://www.rockauto.com/en/parts/de...regulator,6124
As a bonus, its even cross listed to the 1800E in the product reference literature.