In more formal terms, a 1N914 germanium diode, also called a switching diode, are the little glass-encapsulated ones; the little black ones would most commonly be a 1N4001, 1N4002, 1N4003 (these are all the same basic silicon diode with progressively higher reverse voltage specs, which is irrelevant since we use voltages less than will blow any of them) light power diodes.

As long as they are just plain diodes, probably any one will do because the voltages and currents we deal with are very small in the world of diodes.