Is there any way you can get permission to use a copyrighted image? TIA
Sure, contact the copyright owner (and pay a user fee, if required). But I'm sure this is much easier said than done.
An easier and faster (legal) solution would be to buy an edible image from an authorized distributor.
Sorry, this probably isn't what you wanted to hear.
If you have a licensed business, you can register with Deco Pac to purchase the kits and images for many licensed characters.
Other than that, the best you can do is make the cake an appropriate color and add a toy purchased by the customer.