Search "OEM Honda Motorcycle Parts." You will find Partzilla and many others. Search for your year, then GL1500CT Valkyrie Tour. Then select the Carburetor Components diagram. It is usually part number 18. I see prices ranging from $118 to $140 each. Since there are 6 of them, that is a big investment unless yours are destroyed. Spraying carb cleaner into the carbs with the diaphragms, and the Air Cut Valves installed has been known to destroy the rubber.
I have rebuilt over 60 sets of carbs and rarely find the Vacuum pistons bad. Same with ACVs.
I have seen the Vacuum diaphragms with a wavey surface and thought they might not work. I put them together and ran the carbs on my test engine. They balance and tune just like the smooth ones.
