Use a contour gauge for can-do duplicates
A contour gauge contains a row of metal or plastic pins trapped between two sides. The sides provide just enough friction on the pins to allow them to slide when pressed, and then hold them in position. Press the tips of the pins against an existing profile, then hold the gauge against your work-in-progress to see how it compares. Gauges come in various lengths, but a 6" and a 10" gauge should serve most of your needs. You can buy them at woodmagazine.com/ contourgauges.