Make your own up. The original LR items are 0.5mm thick (you fit more than one if you need more clearance) but you dont need to be too accurate. So long as the nose of the sensor does not contact the flywheel you'll be fine. You are looking for a final running gap of about 1.5mm.
If you have any engineering measuring tools then you can accurately measure the distance from the sensor mounting face in the bell housing to the flywheel making sure your indicator does not go down into one of the 36 drillings spaced around the flywheel. Take measurements in at least six (the more the better) equally spaced places around the flywheel and record them. Then accurately measure the sensor mounting face to sensor tip and deduct this from your previous smallest measurement. If the result is less than 1.5mm then you need to add the appropriate sized shim between the sensor and the bell housing mounting face to give you the required clearance. This gives you a starting point as to how thick a spacer to add.
If the result of your careful measuring and calculations is 1.5mm or larger then you dont need any shims.
In all cases mark the end of the sensor with a marker pen, fit the sensor without its O ring and mounting screw, then turn the engine over carefully by hand a few times. If you can get somebody else to turn the engine while you keep your fingers on the sensor you will feel if it is rubbing (it should not be if you measured properly). Take out the sensor and have a good look for any signs of interference. If there are no marks in the marker and your previous calculations are accurate then you are good to go. Clean the sensor tip before you fit it. My CP sensor has no shims fitted and neither did my previous engine.