I use the Internet Archive quite a bit and coincidentally heard a fascinating podcast, an interview with Jason Scott about its history and work, sources etc, a few days ago. So I’ve had a snoop around but couldn’t find anything re Chestnut Grove Quartet and radio recordings. However, there are lots of user groups for old time radio on the archive so a deeper search might find some relevant sources. A direct approach to the Archive might be worth your while as they have so much material there could be broadcasts pending / stored etc. I did get a hit from the Chestnut Grove Quartet, via some recordings they made but the tracks are only short samples. But they give a fascinating snapshot of what was obviously a very good group. YouTube has a more extensive selection…

Internet Archive

Good hunting!