If you are talking about just the mouthpiece itself on the VDH DSV then any mouthpiece that fist a single hose reg will fit the DSV.
If you are talking about replacing the DSV entirely with a DH mouthpiece (complete with wagon wheels and mushroom valves) then any 1.5" DH mouthpiece will work. The first Kraken Series had a USD curved mouthpiece on it. Rob at The Scuba Museum has them in stock.
"The diver who collects specimens of underwater life has fun and becomes a keen underwater observer. .. seek slow-moving or attached organisms such as corals, starfish, or shelled creatures." (Golden Guide to Scuba Diving, 1968)