Where can I find someone to repair my musical Christmas decoration

Do a search for "electronic repairs" and your hometown in Google and you should find someone with the skills to do so. Whether they want to work on your decoration, I can't say. Most techs don't like working on low-cost, unknown devices because you can easily spend hours try to figure things out when you have no schematics or anything else to guide you. Additionally, the cost of such repairs usually surpasses the monetary value of the device. Unless there is an emotional link, most people just don't want to pay for these repairs.

Good luck!