The Adafruit solution below looks like a good suggestion if you need something pre-built. However if you're interested in the DIY approch, you could also take a look at something like https://www.ebay.com/itm/404254884824

Pair this with an arduino nano and you'll have a fairly compact programmable device (I assume for your purposes, you only need mono output). You could also add a lithium-ion battery, solar panel, and charge controller to make something completely self-contained, but that would take a bit more work to figure out how much power is required to play each recording, and how many times per day you want to be able to play them so you can have enough battery power and a large enough solar panel to keep them charged.

Also remember to put your speakers in a box as that will make a huge difference in the volume of the sound being played.