As an FYI I purchased a 10 lb aluminum c02 tank with a brand new 'top' including the cga fitting, the valve, and a new perma seal tossed in..
It came filled (duh) and the total price was $85. It is painted RED, but I like it I will clean up and paint black most likely...
I thought this a great bargain.
They will tap and thread my OTHER 10 lb so it will accept permaseals as well. It should be empty soon so they can do that empty and refill.
So, then I will have a 10 lb for the 180 and the 220, plus a 5lb spare that I can plug into either tank when needed.
This was from a business that sells and maintains fire equipment.