If you have proof you bought it, not your ex, this sounds more like a matter for the police or small claims court. The key word here is "conversion" - the legal definition for assuming control of property which doesn't belong to you. It's akin to theft.
https
/www.nolo.com/legal-encyclopedia/free-books/living-together-book/chapter10-1.html
Try the police first (bring proof that you purchased the TV, not your ex). If they won't help because the property value is not large enough, you may have to resort to small claims court. There's a small filing fee, but it will force your ex to either respond to the court order (in which case you should win if you have proof the TV is yours), or you will win a default judgment if the ex ignores...