Does the Gevalia Crema have milk or cream in it? If so, I don't think there is anything similar offered for the Keurig.
If you read the instruction manual closely, it says something about running hot water through the machine after using the hot cocoa mix because the powder or syrup could clog the internal pipes of the Keurig. Because of this, I doubt anything that could potentially damage the machine would be offered.
There are over (200?) K-Cup varieties available, most of which you can order online through coffee wholesalers. I've also found that K-Cups are MUCH more widely available than T-Discs. I'm sure you will be able to find something you like.
Simon