This is the same rifle as the Mossberg 810.
Made by Mossberg during the 1970s. Depending on condition, $175-$275. sales@countrygunsmith.net
You may be able to find a magazine for a Western Field model M730 30-06 bolt action rifle by checking with gun shops, online gun parts retailers, or auction sites like eBay. It's important to ensure you are purchasing a magazine that is compatible with your specific rifle model to avoid any issues.
Try the tables at egunparts