I don't recall the diameter offhand, but ordinary US brake line will work. It is very corrosion resistant (if you don't damage the terne coating) and a whole lot cheaper than stainless.
I've never cared much for stainless, after seeing just how easily it can rust. Used to have a summer job in a fertilizer plant, and rusty, leaking SS tanks & lines were quite common. If it didn't rust at all, I suppose they would have named it stainproof /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
SS also has other issues, like work hardening and a severe tendency to gall in threads. The extra chrome in the alloy also generally makes it weaker and more brittle than carbon steel ... which is why stainless kitchen knives don't hold an edge nearly as well as carbon steel.
Just my $.02 - - - What this forum needs is an emoticon for Nomex undies !
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