Here is a Waterway Plastics Spa 2" Diverter Cap. This cap is for one of the most common and popular Spa Diverter Valves made, found on too many brands to list. Look for the word Buttress to be stamped on the back of the cap.
Note: To be sure you have the correct cap to fit for your thread, please be sure the word BUTTRESS is stamped onto the back of the your Waterway valve cap. If it does not say Buttress, then you are purchasing the wrong cap. You will need a Non-Buttress Cap.