There is no "gold" edition.
What happened is as follows. There was a pre-release edition of BG2 that had a bonus CD. This CD had one of the 2 extra merchants. (which one I don't now.) There was also a Collector's Edition of BG2 that was available in some stores. This version had a CD that had the other extra merchant.
Both of the merchants are actually in the version of the game that you already have, except that you cannot gain access to them without having some thing from these bonus CDs to unlock them.
The files from both CDs are available on the web, although exactly where I don't know at the moment. I'd try starting at the Ironworks site
http://www.tgeweb.com/ironworks/baldursgate2
There's also a BG2 web ring that I'd suggest looking into. No doubt someone on that ring has links to the files.