One more thing, the official name is Brightside Polyurethane. That's the one you want.

I think they have another paint which is called Brightside traditional enamel.

Don't know the best place on the web to purchase. Just do a Google search for Interlux Brightside and compare prices. There are even some people on eBay who sell it from time to time. Some places on the web only have limited colors.

If you happen to live near a body of water, find a local boat supply house (like West Marine). They will probably have it on the shelves. If they do, they will probably also have a paint chip card so you see what the colors really look like. They will likely also have smaller cans so you can purchase just to try it out -- then buy more in bigger quantities on-line once you decide exactly what you want.