The Fusion P-Series shown above will fit on just about any tower, and is quite a bit less expensive than the OEM Mastercraft Rack.
Unfortunately, the new Mastercraft rack is designed to mount directly to the billet cross member that is built into the new Zero Flex Flyer towers, so it won't retrofit to the round tube like you have.
If you want a clamping style rack, right now the P-Series is the only option. We should be receiving our first shipment within the next two weeks, so we'll have full media and video at that point.
If you have any other questions, let me know.