Mycareer player shoe updates for existing saves

How can I update the player shoes in my existing save, is there a way to do it without starting a new career?

if you mean any players except yours and you on PC, then you can do this using Limnono's trainer. just hit F1 for activating the trainer and F3 for enabling additional menus, then you can go to Roster screen, click on desired player and there will be menus like in MyGM etc. where you can edit attributes and accessories and shoes