There are 5 Goukens, with degrees of difficulty to get.
Regular Gouken (Gray Gi) is easy enough as he was limited to like 2000 in the states, but was also sold over seas in China and such.
Battle Cry Gouken (Gray Gi) was also limited to 2000, but I don't think he was sold outside Toyrocket.com as an exclusive.
Final Battle Gouken (Gray Gi, Dirty) was limited to 500, also a Toyrocket exclusive, and I've never seen any sold by other vendors or Hong Kong sellers except for set lots.
Spirit of Gouken (Translucent) was limited to 300 at Toyrocket as well, but there have been a huge number surfacing from Hong Kong sellers, indicating either a limited release overseas, or bootlegs. Mine had the Toyrocket exclusive sticker so I know mines legit.
Battle Cry Gouken (Gold Gi) is the hardest to find, also limited to 300, but was a Sota webstore exclusive, However I've seen a few cases where Hong Kong sellers were claiming to sell the Gold Gouken in sets with the other 4 variants. Possibly overstock from the factory, but I believe bootlegs. As the Factories Sota was using around this time were just evil, bootlegging tons of their stuff. Never seen any real pictures, and all these sellers used stock photos. I totally missed this figure when he was on sale, but by an extremely limited chance, Sota sent their last one to me as a replacement for the first Broken Battle Damage Gouken I had received from Toyrocket. I was thrilled when I opened the package.

He has Red Kanji on his back as well, and is the best Gouken for sure. last I saw one, it went for nearly $100 bucks on eGay MOC.

That was a couple months ago. The only one on eBay right now is $139.99 BIN.