It was available at the local parts store here in Oz, it's looks like 5/16" rubber fuel line but it is specially made to resist the heat of the trans fluid. It has 'transmission cooler line' stamped into it every few inches, thats about all the info I have on it.
There is not a huge amount of pressure in these lines so there is little need for super high pressure hydraulic type lines and fittings. these cooler lines don't run anywhere near the internal working pressures of the trans.
