Hello,
CodeWarrior comes for free with a conversion utility as well (it converts to multiple formats, is as well able to combine .s19 files, etc). It runs as standalone utility too. Have a look at the prog\burner.exe. You can run it with a GUI or using a command line interface. See as well Help\pdf\manual_burner.pdf or how it is used in Codewarrior projects (it can use .bbl (batch burner language) input files.
Erich