If you like to wear a hat while flying, odds are you probably have to pull it off every now and then to wipe sweat off your brow.
To take care of that problem, pilots can stick a new disposable NoSweat liner into their hat to not only instantly wick away sweat but prevent stains, odors, and the need to keep replacing their hats.

The liners are thin and breathable, so they won’t become a distraction and add just the right amount of cushion between your forehead and the band of the hat for maximum comfort, according to company officials.
NoSweat liners peel and stick to the inside of headwear and feature SweatLock technology engineered to instantly absorb sweat. Moisture is locked inside the liner to help prevent dripping sweat, fogging, sweat stains, acne, and odor. Each NoSweat liner absorbs around 2 ounces of sweat.

Depending on the person and activities being performed, each liner can last anywhere from one round of golf to two weeks of standard hat usage. The liners also preserve hats and keep the inside looking as fresh as the day it was bought, company officials note.

NoSweat liners are available for hats, helmets, hardhats, and visors and start at $6.99 for a pack of three and $34.99 for a pack of 25.
Another way of acquiring buttonless hats is to join AOPA. They periodically send
their hat which does not have that annoying button.
You can also buy them from AOPA at Oshkosh, Sun n Fun, or through their website.
I have been a member since 1979, so I have “a few”.
Thanks Jim, nice going…
And to get rid of that annoying button that drills into your skull under your headset band?…..
Take a pair of diagonal cutters, carefully place them below either side of the bottom edges of the button, and slowly squeeze them closed. Then watch in amazement as the button rises and detaches itself from the cap. Next, gently remove the bottom piece of the button fastener from inside the cap.
Voila!….Button be gone. If you’re worried about any fraying from the small hole left in the top of the cap, a small drop of super glue can prevent that.
A “cheap pilot” (redundant?) friend showed me this trick, because he’s too thrifty to buy a new button-less cap. I’ve successfully neutered all my caps, and now wear them comfortably!