If you are a little familiar with Excel, you can create own kmz-files with the help of this video tutorial. You will need the Excel spreadsheet and the dummy kml file. The Excel files are all zipped to reduce the file size. Make sure to unzip the zip file if you want to work in the Excel table, a detailed tutorial is available here (video guide).

Double-clicking on the zip file and a further double-click on the Excel file which is included will result in a temporary file that you can not save properly.

Do it the right way:

click the right mouse button on the zip file
Chose "Unzip" (maybe called different on the various operating systems, such as "extract" etc.)
in the same directory should now be one identically named Excel file, which now you can double-clicked to open