At least in government, that sort of thing is usually handled with second-source agreements as a contingency of a supply contract. Can have the side benefit of introducing some competition. See AMD, once-second-source-supplier for Intel, Fairchild, and National Semiconductor.
Sure, and for some stuff this is done now. But there are something like 9,000 different pharmacy items (leaving aside medical supplies like sterile bandages, which are procured through a totally different system) in my wife's very small hospital (that ships out all the difficult cases, requiring specialized medicines, to larger nearby hospitals). Should there be second-source agreements- and extra productions lines- ready to go for all of them?
Most of these medicines are like sodium bicarb- the national population doesn't need that much, but if you need it, it's hard to get a good substitute. Snake antivenom or daraprim are good examples of these niche products that are even more crucial than bicarb, but still probably not used enough for any one organization to be able to justify a second-source contract.
