Where I live, there are over 1,000 thumb pianos that I have made with kids in schools as well as churches where I have been the music person. I made all of the kits and the kids put them together. No kid has ever had to pay for one. Most of them have twelve notes and are tuned diatonically, which means that you can actually play real, western world melodies on them, unlike those that originated in Africa. The resonating chambers of these thumb pianos were small boxes rather than the board used for resonating like the ones you are talking about.
There are now many sources for thumb pianos online. All you would need to do is put thumb piano kits into a Google search.
Thumb Piano Kits - Google Search
Are you wanting to purchase completed instruments or make them yourself? From what you have posted, it sounds like you want to purchase completed instruments and then decorate them.
If you want to know how to make the one that you are describing, then I can definitely help you with that. Making them is not hard to do. Anyone can do it.
Please let me know. Thank you!