I know this might not be what you'd want, but I'm doing this with fzf[0]. I have something like this as an alias:

  eval (cat ~/.local/share/fish/fish_history | grep 'cmd:' | cut -c8- | fzf --tac)

and then I simply bound it with `\cr`. It doesn't exactly replace Ctrl-R functionality but it suits my need.

[0] https://github.com/junegunn/fzf