i'm guessing you're trying to make the brittle bone broadsword? i was getting really mad about that one. turns out, it is in raden city but they have it listed incorrectly. if you go through the items you don't see anything called brittle bone under broadswords.. but if you look at the materials, the brittle bone broadsword blueprint is listed as required to make one of them (baston's forte, i think). when the item is crafted, it's not called brittle bone, either. this took me a lot of frustration and several trips to all the cities.
i hope this helps anyone that is having the same problem i was