This is not an item that the Windurst Cooking Guild stocks (Chomo Jinjahl/Kopopo), despite the wiki/ffxiah listings. This is only sold IF a player sold it to them first. Otherwise, farming/gardening only.
I still see a lot of new players ask where to farm to make some gil; North Gustaberg is great. Goblin Thugs drop the Wild Onion, along with gob armor and masks. Bees, worms, sheep, gobs = good gil for starters. Hope this helps someone!
not to copy what Vegetaspride said but, the ruins at J-7 have the largest drop rate on wild onions and the goblin thugs are all very close to each other
The best farming spot that I have found is in the outer horutoto ruins, on the lower right corner of the map on East Sarutabaruta.
I'd spend my time here if there weren't onions on the auction house, though the drop rate is not the best you can get one or even two stacks per hour.
