Within the GLFS instructions, each package has two references for finding the source files for the package—an HTTP link and an FTP link (some packages may only list one of these links). Every effort has been made to ensure that these links are accurate. However, the World Wide Web is in continuous flux. Packages are sometimes moved or updated and the exact URL specified is not always available.
The BLFS Team noticed this problem with BLFS, so they, with the assistance of Oregon State University Open Source Lab, have made an HTTP/FTP site available through world wide mirrors. See https://www.linuxfromscratch.org/blfs/download.html#sources for a list. These sites have all the sources of the exact versions of the packages used in BLFS. If you can't find the BLFS or GLFS package you need at the listed addresses, get it from these sites.
We would like to ask a favor, however. Although this is a public resource for you to use, please do not abuse it. They have already had one unthinking individual download over 3 GB of data, including multiple copies of the same files that are placed at different locations (via symlinks) to make finding the right package easier. This person clearly did not know what files he needed and downloaded everything. The best place to download files is the site or sites set up by the source code developer. Please try there first.
As for GLFS, some packages listed here are not on BLFS or their site. In such a case, we do not have a solution at the moment besides going to the developer(s) and/or their website.
Obtaining all the source packages all at once is not recommended as you will probably pull in packages you won't want. However, it is certainly a convenient option if you have the disk space to spare. First navigate to to the directory you want the downloaded source code and patches to be, then download wget-list. After that, download the packages and patches by doing the following:
wget -N --input-file=wget-list --continue ln -sv v0.70.1.tar.gz rust-bindgen-0.70.1.tar.gz ln -sv v18.1.4.tar.gz SPIRV-LLVM-Translator-18.1.4.tar.gz ln -sv 0.8.0.tar.gz seatd-0.8.0.tar.gz