Radiator Cap for a 1999 Mountain Max

Hi

Does anyone know of a cross over from the Yamaha part to an aftermarket Stant radiator cap for a 1999 Mountain Max. I want the cap but I also want an adapter to pressure test the cooling system. I have a Stant pressure tester but no adapter. I can find the correct adapter I had the part number for the Stant cap.

Thanks for any help.
John

Radiator Cap for a 1999 Mountain Max