There is a way of making your own, if you can get hold of ascorbic acid and add baking soda to it and make your own sodium ascorbate. I can find the recipe to that. Let me know if you're interested. It's not quite like the vitamin C that contains a mixture of these things, plus rose hips and rutin etc. But it's still good!

If you can handle fruit? Those foods are good sources, as are tomatoes, lemons etc.