Rotating electrical contact - solution?

Hi all,
Sorry if this may be more of an engineering question, but maybe
someone here has some experience of this.
I am making a toy for my son. There is a small motor which drives a
propeller, which makes part of the toy spin. The motor is mounted on
this spinning part. The power source cannot be mounted on this part.
So I need to make an electrical contact between a spinning part and a
static part. I am not sure how to do this reliably, and with the
minimum of friction.
Any ideas?
Thanks

.

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