Comment by fxj

There are still several companies who build it. Get one from Doepfer (German Manufacturer) here and connect it to a modular system or a semi-modular synth like a mini moog.

https://www.thomann.de/de/doepfer_a178.htm

https://doepfer.de/a178.htm

live in action: https://youtu.be/1mIferngPqY

or from stylophone:

https://www.thomann.de/de/duebreq_stylophone_theremin.htm

live in action: https://youtu.be/NNn-se0S4Ww