Ditto on what Grant said but Izzy Swan made a simple Oscillating spindle sander a few years ago that might be worth a look. I seem to recall seeing some that use a windshield wiper motor to make it oscillate as well.
Shopnotes issue 127 has a really simple box for DC for using the drill press. In the same article, they rigged up a foot pedal that uses a pulley and some rope or cable to move the spindle up and down. Kind of a funny idea but it might actually work.
My Delta edge sander has an adapter on the end roller that accepts different size spindles, although it doesn't oscillate. May be a quick/easy edition for your edge sander.
You can see it in this google image.
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