As an aside to this thread:
This is a good example of having a local dealer and having a good rapport with.
It helps to open an account, no matter what level of purchases you have. It can get you better pricing. MOST IMPORTANTLY, it makes a huge difference when something comes into question like this. They are not going to do something that is illegal or not within the rules, but there is always wiggle room in almost all situations.
Attitude, rapport, and patronage have a lot to do with times when you need a friend.
This also comes into play when asking for professional advice, service information, and where the fish are biting. Get to know them, and chat with them while shopping and spending.
Find a good shop. Do business there. Realize that they are there to make money, and realize YES, you can get it cheaper on ebay, but ebay won't help you if you have a problem with a cylinder. I have had cylinders leak, I took them back, and they gave me a full cylinder, no charge, no questions asked, thank you very much.
And sometimes, like the doctor, they won't tell you what you want to hear. But, they'll give you the straight short answer.
Steve