Audio Record and Playback Device with Keypad - Needs to be simple

I am looking for a bespoke tech option for a project I am working on - the project involves designing an interactive lesson. The device will be used by students like a phone - it MUST have a keypad - students will be set tasks and must call various numbers on the device to hear pre-recorded messages and get clues and information about their challenge. e.g. 123 - "Hi my name is tom, how are you?" 254- "Have you thought about checking the posters for information?" The device must be about the size of a field phone or walkie-talkie. We must be able to load up to 50 pre-recorded messages onto the device, all of which can be triggered/played back by calling different numbers. Each recording will be no longer than 40 seconds. The device needs to be robust (it's for kids) - preferably the memory storage will allow us to switch recordings in and out relatively easily - however this is no an absolute requirement. I need a total of - 200 devices - all identical Thanks