Rabbit/Jetta/Golf/Fox/Scirocco '77-92: Fuel injection components for Volkswagen. Fuel pressure accumulator, fuel pressure gauge kit, injector O-rings and insulators 1977-99.5
At the end of the day, the guts of the accumulator don't vary much... it's just pressure and volume, and I'm betting there isn't a huge variance there... maybe none that apply to a Saab given it's a smaller motor running standard pressures. The bigger issue is probably going to be shape and fittings, but you should be able to make adapters, or replace the ends on the factory lines (although it'd be a little painful!).