Are there any "natural" vasodilators?

Sure.: But, for what purpose? Nitrates (for example found in beetroot juice) & folic acid can possibly lower blood pressure at least in part via vasodilation. Niacin has been used to lower lipids and is well known as a powerful vasodilator, causing intense flushing in many people, and perhaps has an anti-hypertension effect. If we know what you want to do, we can probably answer better.