Here's a site, maintained by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) in Japan (thus the inclusion of various algae and so many different types of fish), which gives AA content of foods:
Whole Food Catalog: Arachidonic Acid Content Of Foods
Just a few images I picked up of common foods here in the US. Lots more on their site:
Since arachidonic acid is a fatty acid, it's found in higher amounts in fattier foods. There is very little in the low-fat egg white but lots in the yolk. And fish, having so much unsaturated fat (AA is very unsaturated), is a good source. Because AA is a fat, it renders when cooked. Thus, heated foods where the fat is drained away have less than their raw counterpart. That also makes measuring the amount in foods difficult.