This looks like the speaker that goes into your ear, but I meant the one at the bottom of your phone that activates when you switch to "speaker phone". They usually have the keyword "buzzer" in the title of sites that sell them to distinguish them from the earpiece.
Some have just two contacts you can easily solder speaker cables to, just avoid the ones with complicated connectors. You don't need to enclose it to get good sound, it already has an enclosure. I often choose plush toys with a simple MP3 SD player (1€ on Aliexpress, eg https://www.aliexpress.com/item/32657798948.html) and some triggering mechanism.
So then how do you attach/enclose this tiny speaker?