- Edited
Not recommended since the pixel 3 doesn't receive security updates anymore.
But still, if you want to proceed anyway, the zip and its signature are still existing on the official server.
At least it's safer than requesting a zip from a random stranger on Internet ^^
The last Pixel 3 build (i think it is the latest, it is the one i use) is named "blueline-factory-2023020600.zip" and the related signature "blueline-factory-2023020600.zip.sig"
Add the file name in the end of the official url https://releases.grapheneos.org/ and it will download the file from the Grapheneos server.