You can supply power to devices from a powered USB hub, which also allows multiple devices. You can get USB that include a rechargeable batter, for portable applications.
More info here:
https://wiki.mobileread.com/wiki/Kindle_USB_OTG
https://www.mobileread.com/forums/sho...45#post2246045
But here is the definitive work, with multiple USB devices hosted by a K4, which should be portable to newer kindles (original link dead, here is an archive.org link):
https://web.archive.org/web/20120720...off.com/?p=139
But if you plan to try this, read here first:
https://www.mobileread.com/forums/sho...d.php?t=193945