I get "reasonable" results by clamping a long board with a known straight edge to whatever I want to cut, then using the straight board as a simple guide for my circular saw. I don't have a special "jig" or "track." I simply hold the edge of the circular saw against the edge of the board and make the cut. It works reasonably well.
In your case, you will have to do what @woodnthings
suggests: Get a clean straight edge on one side with your "router/jointer", then find a long enough guide board with a perfectly straight edge. Measure very carefully to clamp the straight side of a guide board parallel to the first straight edge. You will need two clamps, one at each end of the guide board. You will also need to use patience and care when measuring and clamping the guide board.
Remember to leave the correct offset for the blade, depending on which direction you will be cutting. Also remember which side of the blade will make the cut edge that you want. The blade has its own thickness (kerf). A fresh, sharp, new blade in the circular saw will make a better, smoother cut, too.
If your circular saw does not leave a smooth enough edge, then use it to cut one or two mm wide. After that, measure and adjust the guide board (still parallel to the first straight edge) to guide the router/jointer to get a cleaner edge.
Practice on scrapwood first.