I don't think you're going to be able to find any pre-order keys from any vendors. Once the game went live, pre-order keys were no longer available.
If you're desperate for access to a black-yellow color crystal, *maybe* you'll be able to find someone selling a pre-order key on eBay. And that's a big maybe.
I'm not sure about that because if I recall correctly, the pre-order code expired like in January. Admittedly its been a while since I've seen that card that I got with the code, but I know it had an expiration date on it. It's possible there are some out there that work, but I'm pretty sure the expiration has passed.