Are you trying to color match for a localized repair? Or are you looking to paint the whole boat? There are websites that say that they match manufacturers colors, but 19 years of exposure, fading, etc., may make that quite a challenge.
If you are just looking for a gallon or two, there are plenty of places that can ship it to you, such as US Composites or FGCI in Florida. Or I am sure there are local boat supply shops that sell it. One option that is frequently overlooked is local boat builders. They typically buy in bulk, and may be willing to sell smaller quantities. This way they can make a small profit, and they also benefit from turning over their stock (there is a shelf life). I get most of my stuff online, at FGCI, or from my local builder.