Best represented that I have found is "air liquide". Even they are only in a handful of countries.
Third world is easier. Make sure you have a lot of adapters and fittings and a good pressure gauge for filling. During my Africa and South America stints my experience is the will fill your bottle if they can hook it up.
That said pure argon is the hardest gas to get. Tig is simply a first world luxury!
Acetalin on the other hand.... they love that in third world countries.
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