Greetings, fellow traveller.
You mean, except Boon Companion (from Seekers of Secrets)?
What do you want your AC for? From your question I gather, that fighting is in the foremost.
If you'd go for a bird for scouting the few levels of druid will matter less (and you save a feat).
That's just what I was looking for thanks.
As a 13th level character with only 3 levels of druid... a 3rd level companion is fragile to the point of uselessness... just showing up gives them a very good chance of being dead.
A 7th level companion has a much better chance of surviving incidental stuff.
A 13th level character with three levels of druid might be better served to have taken a different natures bond option than animal companion. Even with "boon companion" (a feat my GM won't allow, btw) your AC is only going to be as if for a 7th level druid at the cost of a feat that might be better employed.