You can collect tree resin and turn that into pitch/ tar.

It makes such a great glue, that it was used for millennia by stone age men and many generations after that, until recent.

You can use it to reinforce the tip of the feather shaft or attach the tip.

For the tip, I recommend using metal of some sort. Sure, it could also work with (flint) stone, but there’s a reason copper, later bronze, later iron, dominated for that use case. It can be mined and processed relatively “easy”, even without a smeltering furnace, especially copper and bronze.
But that is all another level :)