As this thread is still somewhat new I'll contribute wherre I found the "Gold" package:
I'm using Win 10 and wanted to start playing SH4 again. Had a lot of trouble locating SH4 "Gold Edition" with the U-Boat addition (which, I believe, also includes the v1.5 patch). Amazon did not have stock and Ubisoft was no help either. I eventually discovered the following site which passed my safety checks and appears legit:
https://www.big4shared.com/
Farther down in the SH4 forum you will find my posting that has complete details on installation and avoiding some potential problems.
Best wishes,
Cpt. Hazelwood