I will try to remember next show I see a local guy at, if he has any. He sells alot of Military Surplus. I have bought whole inert 40mm Bofors rounds from him for display. I would not hold your breath, but will give it a shot anyway.
Just curious, are you going to shoot these I assume?
I shoot lead bolts I cast myself out of my 40mm barrel. Would like to use Zinc, but cannot get a good casting with that dang stuff.
Lead casting your own would likely be cheaper than buying 40mm aluminum ones I bet. The aluminum ones are likely not cheap if you can find em..