The basic list of items for sale by all, or most, General Goods Merchants can be found at General Goods Merchants.
This NPC is in a hard-to-find location.
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He appears in Eracus Temple Cavern only at night and is the only mob that sells the Wind Breeze Hot Spice, which is required for Design: Hot Crestlich Dumpling. During the day he is at Eltnen Observatory but is not open for business.
He seems to have multiple spawn points and moves frequently. the best way to find him when you need him is to fly around the edges of the cavern, at about mid-height, at night, and watch for a blue dot on your mini-map.