Hello Adrian,
If you want to search for music that is written for that instrumentation, you can check out “Harp Music Bibliography, Chamber Music and Concerto” by Mark Palkovic. It has a list of many chamber pieces with instrumentation. However, it doesn’t have stories or much descriptions on each pieces.
In “Nineteenth and Twentieth Century Harpists- a bio-critical sourcebook” by Wenonah Milton Govea, you can also find some information and second sources about Pierre Jamet. And I think contacting Marie-Claire Jamet would be a great idea to your research.
I also did some poked around and found a recording:
Hope this helps!