The 2021 update of the RPi Zero 2 W at $15 is an interesting board. It only has 512k mem and no USB sockets. I’m pretty sure it could run the GoPiGo3 but possibly not the desktop of GoPiGoOS.
If @jimrh isn’t able to pickup a Pi5, perhaps he will grab a Pi Zero 2 W to try with GoPiGo3 Charlie or Charlene.