These are all free from several sources on the Internet. Gumroad and Artstation being the most populated, some can be found via an internet search for Free Shaderball. Word of warning, these are available in various formats, the most common of which is 3DSMax and Cinema4D. So if you don’t use either of those, you will need to get somebody you know who has this software to convert them to FBX. It’s not a lot of hassle, quite simply just selecting the models and exporting them. It’s entirely possible though that you will find what you want available in a format you can use.