I simply replaced both of my valves with off-the-shelf parts. (Valterra, but THETFORD a better choice).
Take a picture and head over to CAMPER CAPITOL on Forest Lane. Great parts house. Bring your list of other items, or samples, of all the small stuff you need or are missing (door latch, curtain roller, etc, etc). Buy the catalog.
1990 35' Silver Streak Sterling
; 9k GVWR.
2004 DODGE Cummins 305/555; 6-manual; 9k GVWR.
Hensley Arrow. 10-cpm solo, 18-cpm towing
Sold: Silver Streak Model 3411