I am a HUGE fan of George Harmon Coxe, and have read a number of his mysteries. Interestingly, Flash Casey is not his only newspaper photographer cum amateur sleuth. His first (and arguably, his best) is a character named Kent Murdock. He appeared in many, many mores stories than Flash Casey did. The novels are uniformly excellent. I don't think the character was ever in any other media. I've always found it odd that you'd have two characters that were identical in so many ways, but what do i know?
Interestingly, it was a cassette of Casey Crime Photographer ("Christmas Shopping", which we listen to faithfully, every holiday season - I know it like the back of my hand) that got me into old time radio, which got me into crime novels of the 1930's-1950's, which got me into early television crime shows, which... one dot connects to another.
There was also a novel about Casey, Ann Williams and Ethelbert, entitled Dead Heat (1950), by Paul Ayres. A 'novelization', based on one of the radio episodes. I know which one, but can't remember just now. See the photo attached.
I've had the book for well over a decade but have yet to read it. Once I'm done 'Boys Will Be Boys" (1947), maybe I'll crack the spine of this one. We shall see.