OK - I'm not positive if I know what watermelon radishes are. But I have seen beautiful radishes that are watermelon colored inside at the Headhouse Farmers Market (2nd and Pine Streets). The market will be there for two more Sundays (Dec. 13 and 20th). However, last Sunday was the last week for one of the vegetable vendors (the first one on the end), and he may have been one of the ones with the "watermelon" radishes. But it's possible that other vendors had them, too. I just can't remember for sure because I have never gotten them. Good luck.