What about something like this?
https://www.aliexpress.com/item/4M-LED-Christmas-Holiday-LED-Light-Battery-Powered-Led-String-Lights-for-Home-Garden-Party-Decoration/32866555230.html
Peel off all the foofy stuff, leaving just the wires and LEDs, bend the wires between LEDs into ‘Z’ shapes to shorten as needed, rewrap in clear tape to insulate them, then in another layer of clear tape to stick ’em on your sneakers.