Giving a quick update: this is going to be slightly more complicated than I thought.
I'm assuming you're working off of the code that was provided from this Reddit thread: https://bit.ly/2Hsdp1d
If so, then the big thing to figure out is how to replicate the file structure of Doki Doki Literature Club (DDLC). As it currently stands, that piece of code will try to look inside the .app file for the Mac, whereas you want the file to be generated on the same level as the .app file. This means that you'll want to replicate the file structure of DDLC. A quick examination on Steam shows that it packages a .app file separately from the rest of its scripts and resources, so that way basedir will be able to find the .app file. Maybe someone who is more proficient with Ren'py can help with this, as it seems like a potential paradigm that can be repeated for file distribution. Otherwise, I'll try taking a stab at this later.