I got a kick out of this one. The author builds the standard drum sander like build for the drill press, but then attaches a motor to the crank for the shaft for the drill press to have it go up and down…me…well it works, and it is cheap…seems a bit overkill.
https://www.instructables.com/id/Oscillating-Spindle-Sander-From-a-Massage-Pillow-a/