Sent a first class international package and it was never delivered, what are ways to get my money back

For context I sell clothing online and I sold an item to Croatia. Two months pass and it hasn’t arrived. I filed a missing item claim a month ago (silence) and called USPS asking if the item will ever arrive and they said they don’t know and the tracking will only go up to when the item leaves the country (USA). I also can’t get reimbursed (it was $350 btw) since I don’t have insurance. What do I do to get the money back! Should I send another empty package with insurance and hope it doesn’t get delivered so I can get money back?