These hypos can be found scattered about the world, and can be purchased occasionally from varying Replicators. They do not, however, drop from enemies, and are therefore limited to location and purchasing.
Dr. Marie Delacroix, Chief Engineer aboard the Von Braun, was well aware of the imperfections inherent in the rushed development of the ship. Notably, the coolant system of the ship had a chronic cracking problem, leading to the widespread leakage of hazardous materials. While these leaks are easily detected and usually quickly fixed, she demanded that an excess supply of ChemCal rad hypos be distributed throughout the ship. Unlike most of her cautions regarding conditions on the Von Braun was actually heeded.