This image was adapted from a picture posted to publicdomainq.net. All of the images on these sites are in the public domain i.e. CC0. This site is only in Japanese but can be easily navigated with Google Translate.
男子 - 體育老師
cute people、exercise、health、JMC、male、Male Characters、man、Manga、physical、physical education、publicdomainq.net、school、sport、sweat、teacher、train、training、whistle
可愛的人、行使、健康、JMC、男、男性角色、人、漫畫、物理、體育、public domain Q.net、學校、運動、汗、老師、培養、訓練、哨
資料來源：openclipart ( https://openclipart.org/ )