There are 2 ways to add/purchase Sierra Wireless X-Cards. They can be procured:
Manufacturer Direct: Card installed at Sierra Wireless at time of purchase
Purchased and Installed by USATCORP. USAT is an authorized distributor and integrator of Sierra Wireless X-Cards. By going through USAT you will remove the hassle of integration and have the peace of mind that your warranty has not been voided.