Convert GBC .srm + .rtc to .sav?

I’m trying to convert a save of Pokémon Crystal so I can open it on an emulator that has link capabilities (TGB, in this case). The problem is that RetroArch uses .srm files (as well as a .rtc file for the internal clock), and TGB uses .sav files.

I tried renaming the extension, but that didn’t work.

Does anyone know how to do this? Thanks in advance.