91 Q45 Steering pump control valve... Blocked

[Desmoquattro]

I stripped down my steering pump on my 91 Q and discovered that the control valve is blocked solid. It's the cylindrical unit that is spring-loaded and located just ahead of the banjo bolt for the oil line. As far as I can tell, there is no way to take it apart (without a lot of force anyway). Anyone know of a source for a new/used one? All I have seen are complete pump assemblies.

PS if anyone knows what the pump is interchangeable with (as in what other Nissan's might use the same pump) it would be helpful... Not many junkyards stock Q45s around here...