Black and Decker (Van Dorn) has about the worst parts availability and service for its industrial/commercial valve service stuff that I have ever seen.
Back in the seventies I needed a few parts for a seat driver. Only one service place in Michigan and they didn't even know what a stone driver was.
I even called the factory in Towsand Maryland and they would be glad to sell me a new driver for $450.00 but they stocked no service parts there.
I threw out the whole setup and went to Souix. Then to K-W.
You might try Silverseal.com or Goodson.com an automotive machine supplier. Good luck,, but I gave up on Black-Decker stuff, in general
, a long time ago.