I was able to download a copy of SH IV Gold for 10 bucks Canadian from
http://shop.ubi.com I don't know for how long the price will last, most likely it is part of the spring sale.
If you have not done this before, after the download finishes don't click the install button. the whole content of the DVD is in a numbered folder inside "installers" folder. You can burn everything in that folder to a DVD and install the game wherever you want. Your serial number will be emailed to you.
Have fun