My son uses ProLoquo2Go but it is for iPad, so the combo can be expensive.
There are Android alternatives
For these types of apps, plus the games that requires the processing power, you can find a ~$60 Android on tablet on Amazon and save hundreds (there are tablets designed with drop resistant casing already in place, so that $60 tablet saves you another $40 for a case if you bought another). You can buy two and have a backup in case of a break or battery drain and still save hundreds. Just as functional.
FYI, the buttons I have Amazon may have discontinued them sadly. Unfortunately, one of those product lines that doesn't make them enough money. I'm sure something like smartthings has something that can be repurposed for this, but if anyone has ideas, would be good to build some ideas people can work with.
After much searching on Amazon, I found these diapers that were highly rated and from the description and reviews would likely fit my needs.
I only ordered a 10 pack to check for sizing, but you can get them in packs 100 for cheaper per diaper.
I'll test it out and report back.