Please note that since SLES12 SP3 is no longer supported, not even with Long Term Service Pack Support, you will not find an official public download.
Given the compat- prefix to the package name I believe this package was available via the Legacy Module for SLES12 although I do not see it listed when searching https://scc.suse.com/patches#!/ for compat-libgcrypt11 in Legacy Module, version 12.