You can easily make a pattern at a station by cutting a rough cardboard piece and then using a marker mounted in a block to draw a line on the pattern. Cut the line and you should have an almost perfect fit. Sometimes it takes doing this twice once to get close enough to mark with a smaller marker.
Identify stations that are exactly as far apart as the width of insulation foam. Cut patterns to match each station. Glue the patterns to the foam making a many layered sandwich with the foam extending well beyond the patterns. Use a rasp and then sandpaper to trim the foam to meet the patterns. This should give you a smooth mold.
Making one part you can lay up right on it and dig out the mold destructively later. If you want to make more than one part cover the mold with some kind of protection (chipped glass, micro, bondo etc.) and mold release and lay up your part on top of it. Depending on how thick your protection layer will be adjust the diameter of the marker to draw the lines a measured distance from the surface you are matching.