Try these:
Fuel Pressure Regulator Spring
(International) 1823643C1 (federal emissions; 94-98
(International) 1825854C1 (CA emissions; engine serial no. 201681-98
Fuel Pressure Regulator Valve Assembly (contains spring, valve spool & new brass plug)
(Ford) F5TZ-9K061-A (federal emissions; 94-98)
(Ford) F6TZ-9K061-AA (CA emissions; engine serial no. 201681-98)
I've never vouched the correctness (or if you can even get the springs from International), or heard of someone just getting the spring. You could just get the Ford CA regulator above and install the whole thing. Unless you dealer gives you decent prices (list is $35.62, I would get it from someplace like
Tousley Ford Parts ($23.51). Cheers!