You can get coil spring stock from Brownells. However, you can slide that coil spring on the shaft of say, a Phillips screwdriver, then, use a belt sander to lighten it. Hold the spring and driver at a 45 deg angle, and parallel to the belt, then gently place the springs side, the springs coils and not the ends, against the running belt. You'll see the spring spin on the drivers shaft. This will cut the springs OD down a little at a time, and lessen the springs operating pressure. This is the correct way of doing this, and not by cutting it shorter and stretching it.
If you want to make one with spring stock, measure the old ones OD, and the wire diameter. Use a piece of coil spring stock with the same or close OD, but a smaller wire diameter, and the same number of turns per inch, or close. Cut it with a wire cutter, so that the length is a shade longer, then, grind the two ends flat, making it the same length.