Theremin for Disabled brother

Hi all,
Several years ago my family went to Disney World, and my younger brother, who is disabled, discovered a theremin in Figment’s World of Imagination. 
I have NEVER seen him so happy and excited, in his entire life. 
My question to everyone here is: how do I find a theremin that we can get for him, that will be comparable to what he played with in Disney World?
We have tried other, more basic theremins in museums and other places, but they just aren’t what he is looking for. 
He wants different sounds, and different tones, and the ability to play music. 
Personally, I have no knowledge, and have no idea where to start. But it would make him so happy to have something to play with. 
He’s austistic, and has Down syndrome, so he has a hard time relating to people, and is very particular with the sounds he wants. But he loves music. So much. 
My whole family is willing to pitch in, so cost would not be a factor. 
Please direct me on what I need to know, and how to find the best theremin for my little brother. 

Thank you!!

Hi KariStucki,
I have no idea what they may have in Disney World, but perhaps the Moog Theremini is worth looking into, it has 32 different preset sounds, and while the pitch correction is frowned upon by theremin purists it does give various interesting musical scales to play with and I can imagine that might give more musical approachability and structure for your brother. Of course it will still play just monophonic, with a single voice at a time. Besides just doing a search on YouTube for "Theremini", the Clara Venice -Theremin Online interview/Q&A by Theremin Today may be interesting to watch, she primarily uses the Theremini and tells also about using it for workshops/demonstrations for children. Hope this helps.