David Hockney
(1966) 

Nicholas Walter George Wilder (1937 – May 12, 1989) was an American art dealer and owner of an eponymous contemporary art gallery in Los Angeles in the 1960s and 1970s. He later closed his gallery, returned to his native New York, and developed a second career as a painter. 
Wilder was friends with the British artist David Hockney and became Hockney's dealer in California. Hockney depicted Wilder in his 1966 painting Portrait of Nick Wilder. Hockney included a drawing of Wilder in Friends, his 1976 collection of lithographs of acquaintances.

https://en.wikipedia.org/wiki/Nicholas_Wilder

Portrait of Nick Wilder
1966


Acrylic on canvas 
182 x 182 cm
Private collection