Goatskin Breeches

Legs, item level 23. Equip level 23, GLA MRD LNC PLD WAR DRG DRK GNB RPR.

From 126 The Hottest of Box Lunches and 1 more quest.

From quests

126 The Hottest of Box LunchesChoose one of 4
130 Sylphish ConcernsChoose one of 4

Other databases

Eorzea Database (the official one, on The Lodestone)
Console Games Wiki
Garland Tools (vendors, crafting, drops)