Context
An 11th level PC in a game that I DM is a ranger6/rogue3/warlock2. He noticed that his animal companion, a black panther, could use a little boost to her defenses, as she goes down frequently. This is due to the PC's multiclassing and his (preferred) reckless approach to combat (face first).
Note: the animal companion currently has 38 HP with an AC of 14. The ranger (Beast Conclave) is from Unearthed Arcana: The Ranger, revised.
His character, therefore, inquired about armor options for his panther. The particular, visited blacksmith replied that "for the right prize, anything is possible, but [he'll] need some time to craft this".
Now, post-session, I'm looking into existing options from the books, but I can't find any. I own all the books, except for XGTE and the adventure modules.
Question
Do any of the books contain (magic) items for animal companions?
I'm mostly interested in armor, but going through the pages I'm wondering if any such item exists. I also allow sources from Unearthed Arcana, so within the scope of this question I count UA as "any of the books".
If not, I'll homebrew the armor for the PC and might possibly follow up on this question.
Research / Confusion
As Sdjz points out in a comment, there's a question that hints to a "yes" on my question: Can a Beast Master ranger armor their animal companion with barding?
Barding. Barding is armor designed to protect an animal’s head, neck, chest, and body. Any type of armor shown on the Armor table in this chapter can be purchased as barding. The cost is four times the equivalent armor made for humanoids, and it weighs twice as much.
I'm attempting to read up on barding with the PHB in front of me. The index says "under Armor and Shield" so I went to page 144-145. But I don't see any mention of barding, under this section. Am I missing something here?