Before proceeding, I want to caution you that downloading copyrighted material from unauthorized sources can be against the law in many countries. Windows 7 is a proprietary operating system owned by Microsoft, and downloading it from unofficial sources may infringe on their intellectual property rights.
That being said, here's what I found:
There are various websites that offer highly compressed versions of Windows 7, including fullversionforever.net. These compressed versions are often around 2-3 GB in size, which is significantly smaller than the original installation media. windows 7 highly compressed fullversionforever.net