Not that I can think of, but there are single-target buff spells on the bard spell list which might have a similar effect.
Have the ally summon more allies first?
Some archetypes do that.
It's a big part of what makes a Lotus Geisha, for example : the possibility to target a single target, both with beneficial and hostile performances for increased benefits, without losing access to the normal versions.
I believe there's at least another one but I can't remember which one it is.
There aren't that many ways to boost Inspire Courage and the likes period.
It's more going to be about your spell selection at this point. Being able to safely ignore group buffs is not a small thing.
Also, Bards don't have to be bad at fighting. They can be quite decent, you don't have to leave your ally shoulder it all (you can of course, it's just not mandatory).
And now that I'm saying that I'm reminded that Arcane Duelist has its weird weapon enhancing song, and that works best on a single piece of weaponry. It's another possibility. There's a few of those here and there.
Skald also has some similar options.
For a single target, you could also look at other ways to help. Aid another's usual downside is the single targetedness of it, for example, and that's not an issue here. There are a few ways to build at least a bit into it.
There are several magic items that can boost bardic performance:
Dervish Sikke
Inspire Courage +1
Inspire Competence +1
Three Reasons to Live +6 levels for performance
Fascinate 1 target +[1 target per 3 past 1st] => +2 target
Inspire Courage 1+[1 at 5th]+[1 at 11th]+[1 at 17th] cap +4 => +1 maybe
Inspire Greatness 1 ally + [1 ally per 3 past 9th] => +2 ally
Inspire Heroics 1 ally + [1 ally per 3 past 15th] => +2 ally
Banner of the Ancient Kings +4 levels for performance
Inspire Courage 1+[1 at 5th]+[1 at 11th]+[1 at 17th] cap +4 => +1 maybe
/cevah
There are faction feats, master performer and Grand Master performer, each feat gives a bonus, and it applies to everyone