look online. Duplicolor's Metal-Cast Purple looks nice when done right. If you're doing a valve cover, makes sure to use the Metal-Cast "Ground Coat". It provides a nice undercoat finish that makes to anodized color pop.
Check Walmart. they should have some in their automotive section. if not, just go to another parts store. if nothing else, you can order it online as I mentioned before. it'll just take a few days to get in.