All of these cushion your helmet wearing as an added bonus.
Used to wear bike caps, but now I use my Schampa balaclava (one is made in the U.S., one in Mexico). Just bunch up the face mask part on top of your head. Comfortable, and seamless where it goes across your forehead...
Unlike the one under armour skull cap I have used. The seam leaves a mark, but is still not felt - so it's a wash.
edit: Ordered the Halo skull mask and it's got some new fangled 6 inch or so rubber gasket type deal that is not thin and I guess you place it parallel to your forehead so that it keeps sweat from your eyes? Very tight fit also - I'm going to return it for a refund. Amazon, so no worries.
Even the Buff headwear can be used - ff to around 1:52