if you play on console and cant use mods, you can finish the companions questline and craft it at the skyforge. but you have to finish the questline and it has to be done at the skyforge
Now that's interesting. I've never tried to craft some of the other stuff at the skyforge. I'll have to check that out. Do you remember what it's under?
Apparently you can craft something like it or maybe the same but I got it by installing a mod that makes Aela's base armor removable so you can let her wear other items. Then I took those items and gave them to Lydia. The mod is here: [link]