I did similar handle fix years ago.
Started with this, not enough wood for a handle.
Laminated a bunch of strips on to fill out the handle and backed the bow with bamboo.
Shaped the handle.
Years later a guy emailed me and said he bought a bow at a bow shop in Chattanooga Tn with my name on it and wanted to know about the bow. Turns out it was my "Frankenstein" bow. I had sent it to a guy in Penn, how it migrated to Chattanooga is anyone's guess.
Here is the picture that the guy sent me that I recognized as the bow I made.