The Pugilist already has an option built-in for ranged attacks: Proficiency in Hand Crossbows.
You did say you had no intention of going with a sidearm and have heavily invested in melee. That's a perfectly acceptable build decision - but it does have it's drawbacks (no ranged option) that you will need to compensate for in other ways.
You're not always going to be in the spotlight
It's also important to remember that you have a character that excels in martial melee combat. Encountering a flying creature absolutely puts you at a disadvantage - but maybe it's where other party members excel. If you always expect to be able to fight at and with your optimum level, you may get frustrated when things don't go your way. But that's okay, those are opportunities where other party members can step up.
I've played a Great Weapon Fighting Paladin with no ranged options and in those fights against flyers, I sat there throwing spears. It was sub-optimal, but that was because I didn't make a build that was good at ranged.
In those cases, I also found other things to do (helping allies, healing, etc.) that actually helped me realize more about my character and his capabilities.