Can't help you on a internet source for paint but automotive paint isn't cheap. FWIW, acrylic enamel is old technology and would be considered the "cheap stuff" by todays standards.
Also FWIW, all the urethane epoxy primer, base, clear, reducers and catalysts to paint my Barracuda cost just shy of $800.
Been ther , done that. My duster is clear coat base coat and it was way up there. I'm wanting a scource for acrylic enamal(old Tech) to paint a driver. I know there are cheaper places to get the same paint. Where are they?