Last month, while wandering Etsy I found a painter of Portland, Oregon, named Matte Stephens. He do some commercial illustration also. His illustrations are made with gouache. You can find their works in Matteart. They are charming, very retro. The prices range from $35 to $1,000. Internet makes the world smaller. Fifteen years ago it was unthinkable for me to get to him.
My last discovery is an illustrator, Brian Gubicza. He is cheerful and fun, but at the same time he is elegant in the use of colors. He is able to make very expressive pictures with just very geometric and seemingly simple drawings. He sells his artworks at $20.