Without seeing the cooler and the other pieces it would be hard to tell what is required. But to guess it's probably AN-10 but could be AN-8 or AN-12.
I use these guys.
BAT Inc A dealer for plumbing
BAT - MOCAL Oil Control Systems
Both of these links are from the BAT MOCAL site.
This is listed as ALUMINUM SWIVEL HOSE END FITTINGS
http://97.74.32.155/files/ahosend.pdf
THREAD SIZE CHART
http://97.74.32.155/files/tchart.pdf
There are many manufacturers. Aeroquip, Russells and others. I don't believe that Parker makes the aluminum fittings. I'm sure each has specifications on their sites. The AN designation is a specification and all manufacturer's products should connect to another's.
Jim