Both eBay and Craigslist are great places to start. But unless you're sure you're dealing with a reputable seller, you might want to look for other sites that specialize in precious metals. Buy silver bars from an industry leader and take advantage of the most competitive prices and the largest selection on the web. Provident Metals is one of the best gold IRA custodians and sells silver ingots from the world's most famous private mints, such as Johnson Matthey, Northwest Territorial Mint, SilverTowne and many more.