Big Clive does great teardown videos, and I especially appreciate his patient and thorough reverse engineering circuit walkthroughs – and this one is one of the best I’ve seen so far:
I bought this from Banggood, but it’s quite a common device on eBay if you search for USB plasma ball. Once you see that it radiates a very high voltage gradient at high frequency you may choose not to plug it into, or place it near anything expensive….
It’s really nice to see that the circuitry inside has not changed from the original units from many decades ago. If anything the components have improved, making the unit more efficient.
If you like high voltage electronics and plasma then this thing is worth buying just for the PCB inside. It’s very hard to wind reliable high voltage, high frequency transformers like the one used here, so it’s worth every penny just for that little flyback transformer.
Note that it’s best not to use the circuit without a load on the transformer to protect it against excessive open circuit voltage.