When in Mexico I ordered it at a Pool Supply store, they didn't carry it because the calcium level in the local water was high, so no one wants to increase calcium. However, they could order it, and the clerk didn't care if I was screwing up my pool, so I managed to get it. I'll bet it's the same as where you are. They most likely will ask why you want it, tell them you are a teacher (school, church, boy scout) and are using it in an experiment.
My husband also has prostate cancer and he is taking it. It's the easiest and has no troubles in taking it, just a bad smell. If you do manage to get it - do not throw out the bag it comes in, that is the best container to mask the smell, you'll still need to double, triple baggie it though.
I tried to take a unopened bag in my suitcase and TSA took it away from me, I also had a bag in my checked baggage and it wasn't found. They don't bother capsules though.
I am sure customs will stop it also, it's flammable or something like that, not because of us. But if you had it sent UPS or FedEx - there is a chance you will get it as they aren't monitored as closely by customs. But, you'll have to register what it is.... is it a federal crime to lie on a customs declaration? probably