(Is there a way to do this and I just didn't find it yet?)
Yes and no. You can manually decommission the fighters and bombers that your carrier has in its fighter bays and manually order up the next batch of fighters and bombers in whatever balance you want, though you have to do so ship by ship. Moreover, as soon as you start losing fightercraft, the carrier will start replacing the fighters and bombers in a manner that brings the balance back to the 50-50 split (or whatever the default is), rather than keeping the split at what you had set with your manual fighter construction.
E.g., set "build 25% fighters and 75% bombers" as a default.
Bonus if this can be changed on a per-ship/fleet basis. (Maybe just in fleets, from the fleet screen?)
I'd support a fleet setting similar to the one for troop ships, particularly if it includes options for fighters, missile bombers, and torpedo bombers, rather than just fighters and bombers.