It would be nice to be able to keep all those old machines going. In fact I would go as far as saying that there must be a market "out there" for servicing kits for old Boyles type machines. Surely someone must supply them?
Other than that I'm wondering if simple substitution of the regulators (with a more readily available type) is feasible ... perhaps just requiring threaded adaptors, rather that major re-piping. Anyway, I hope you get a result on this one. Be sure to let us know how you get on.
Meanwhile, have you tried Diamedica