Most valve parts are available, because they are made by "third party" companies. It MIGHT be Eljer, but I do not find any Eljer cartridges with that "double D" port configruration, and it is upside down from the Eljer units I can find.
Hi there Nick! I spoke to our (American Standard Brands / Eljer) customer service team and they would like to see more photos and get pictures of the parts (valve, handle, and /or plate) if possible. Can you send your photos or additional information to socialmedia@americanstandard.com ? Eljer is owned by American Standard. you can visit www.Eljer.com - We are waiting for your email so we can help you further. - Gulsah At ASB