As others mentioned, for low frequencies (~1GHz) you can make your own Short, Open, Through and Load, using standard SMA connectors.
The most limited in frequency from all these 4 elements is the Load element, because you do not have the special volume-type resistors (very low parasitic inductance) used by Agilent.
You can do a trick here to minimize the parasitic inductance of your own Load, placing three 150 ohms SMD resistors (0402) in parallel, and solder them carefully from the central pin of the SMA to the ground at 120 degrees. Using a clean soldering I managed to reach 2.5GHz equivalent calibration.