The other good Agility and related skill trainer for your CKO - and my preferred one - can be Frederick, because he starts off with enough STR and power skills to be a competent soldier. So you can start pumping AGI with him asap. Sara needs some power skill investment to be able to score enough kills later on as well for a potentially higher level after all.
Other than that, I prefer to leave companions for more of a secondary skiller (which won't be needed 95% of times), as I tend to spec into Wound Treatment, Surgery, First Aid, Looting, Trade, Engineer, Path-finding and Tactics (only of I don't intend to spec into throwing weapons or bows) myself, so that we get the +4 bonus for these party skills. And of course, I also max Inventory Management, Trainer, Persuasion, Prisoner Management and Leadership at the end of the day, as well as the required power skills and get 6+ AGI skills at least. Achievements and bonuses from books are taken into account as well of course in terms of maxing skills.
All of this is mostly possible with the proper character start for optimal and maximized skill layout (male -> a respectable physician -> apprentice of a local craftsman -> self-employed merchant -> series of unfortunate events), by pumping only for INT from level-ups and leaving STR, AGI and CHA to Elixirs of Arkon. By level 49, I can reach 63 INT this way. Further info for this character progression setup can be read here and at further posts above/below:
https://pop3.fandom.com/wiki/Talk:C...901-20190420094003?permalink=24421#comm-24421
And then Tracking and Spotting can be left to companions...