Yes, Carrier RNA is available separately. It is sold in combination with other buffers in the QIAamp MinElute Virus Accessory Set and the QIAamp Viral RNA Mini Accessory Set.
In addition, Poly-A Carrier RNA by itself, without any buffers, is offered under the following catalog numbers:
•1017647: 12 vials, each containing 1350 µg lyophilized carrier RNA
•1068337: 1 vial containing 310 µg lyophilized carrier RNA