I see Moe posted the Harley one that Brent carries. If that isn't it he could use the same application cap in a different style from any Harley shop or place like J&P Cycles that sells after market stuff. Just have to measure for dash clearance.
The application of the one pictured is: vented RH thread,83 or later XL,FXR,Dyna,Softtail , or Road King.