Many monitors are made buy Original Equipment Manufacturers (OEM’s). This means they buy various components from other suppliers and integrate them into a unique product. There are several large manufactures of loudspeaker drivers such as Audax, Focal, Seas, Vifa, etc for which you can buy replacement voice coil assemblies (I’m assuming we’re talking about dome tweeters). If you’re lucky, your monitors will use a standard model from one of these companies. If so, I can direct you to a source. Sometimes, however, the OEM will have custom components made. In this case you’ll probably have to go to an "authorized dealer" for the repair.
Can you remove the tweeters from the cabinets? If this can be done without destroying anything, write down every letter and number you can find on the back of the driver. Post them and we’ll see if we can figure out what you have and how to fix them.