Not sure if you have this information, but wanted to share Barks.
Our earlier birds, 733, 734, fitted with Parker Hannifin PCU's, were upgraded in the mid-1990's. Nothing more specific yet as to the disposition of our pulled PCU's, however I do have a part number that may assist you in your search. The original Boeing part number for the defective PCU was 65-44861. Later iterations of similar units carried sub-part designations, ie:-01, -02, etc.
You should be able to find some spares out there that, while rebuilt with a new valve assembly and limiter would have the basic design of the original intact.
Additional information from the coverall gang:I've been told de-certified units (of all types) have been known to survive and end up in inventories carried by the third world. Perhaps a look at African, South American, and Near-Eastern sources would be a worthwhile endeavor. Finally, a classic bird that was put to desert sleep prior to 1995 (when PCU replacement was first begun per AD) could be another source. Happy hunting!