I have a D40P it is fitted with a Sparcraft Spring Vang ref 37560020105. Mine suffered corrosion at the base of one of the tube sections but the tubes were long enough to cut the corroded section off and re-rivet the tube to the end fitting. I also needed new sheaves for it and found Eurospars Ltd https://www.eurospars.com/ who stock an extensive range of Sparcraft and Facnor spares.
Good luck with your repairs
Doug Ellis