Using CircuitPython running on a RP2040 Zero, an audio amplifier breakout board, and a small speaker I was able to play mp3 files. Certainly good enough for speak and spell quality audio that I'm trying to replicate on this small scale.

I'll need to figure out how to pump up the volume but this is promising. The board has plenty of room on the back for a speaker and amp circuit yet. The speaker fits perfectly in the handle cutout as is so that is an option too.