D.
I have just been through this with Cat in the Hat. It's not a common theme that's carried in most bakeries. I learned the hard way that bakeries won't copy party supply images because of copyright issues. So if it isn't in their "book" of cakes that they do, you may have a hard time finding someone to do it.
I didn't realize that and waited until the last minute and have had a hard time finding someone to do it for me. You're best bet is to go with an individual baker who does it out of their home. You may find someone who'll be willing to do it.