I ordered mine from Maqam music (they have a web page by the same name) and it cost around $120 including shipment.
The chip I got from Ketron US came with NO instructions. After I figured out how to open the keyboard and installed it, when I started up the Vega, it zapped all my old saved patterns. I had these saved on disk but not in the same order as I had in RAM so my registrations got screwed up.
Before installing for anyone who is thinking about buying it, make sure you save your pattern or write down the order you had them saved in RAM if you use them in your registrations.
There is also a page 2 for the patterns to access after you have used up the first 100 slots. So pattern no. 101 will be under the first button for the Patterns on page 2.