From Sigma:
Canon Mount Firmware 1.03 – It has optimized the lens firmware for SIGMA TELE CONVERTER TC-1401 and TC-2001.
Note: Before upgrading the firmware of 120-300mm F2.8 DG OS HSM S013, please first update your SIGMA Optimization Pro to Ver1.2.0.
Download via Optimization Pro Software and install via Sigma's USB Dock.
B&H carries the Sigma 120-300mm F2.8 DG OS HSM Sports Lens.