microzone, an opto-interrupter is simply a matched pair of light emitter and detector facing each other in a plastic molding that provides a slot through which an opaque object can pass to block or "interrupt" the light path from emitter to detector. Just think of it as a matched pair emitter and detector that the manufacturer has mounted for you to make it unnecessary for you to provide the optimum mounting arrangement to detect objects passing between the pair.
Go to www.digikey.com and search for "optical sensors, then "interrupters."
Or go to www.mouser.com and search "photo-interrupter."
You could also probably use a reflective sensor which has the emitter and detector side-by-side "looking" in the same direction, away from the module. This configuration detects a reflective object passing in front of the module. However, if you can use it, I think the interrupter type would offer more reliable sensing because it does not rely on the reflectivity of the object, just its opacity, while the reflective sensor depends upon the location and reflectivity of the object being detected.
These devices come in a great variety of wavelengths and physical and electronic configurations from simple bare-bones units with emitter and detector leads hanging out to amplified units, photo-darlingtons, photo-SCRs, photo-Triacs, etc., etc. Start out by finding a unit that looks like it fulfils your physical requirements then download the data sheets and application notes and see how they work and how to wire them up.
You haven't given us any info on which to base a recommendation of a vibrator, but go to www.allelectronics.com and search "DCM." DCM is their prefix for DC Motor-xxx part numbers in their catalog. (All Electronics is a surplus store in the Los Angeles area.) They list several tiny vibrator motors intended for use inside pagers and phones, just the types of vibrators you would obtain by disemboweling a phone as suggested by Tedyp.
These are simply small DC motors with eccentric weights on their shafts. If you need more vibratory power than these tiny devices provide (as I suspect you will if you are trying to shake a mechanism rather than a shirt pocket), you can "roll your own" by buying a larger motor and a gear or pulley that fits the shaft and sawing off part of the gear to create an eccentric weight. Try also www.candhsales.com, another surplus store, this one located in Pasadena. They have lots of motors, gears, and pulleys. The amount of "shake" you can generate by this means is limited only by the size of motor you buy and the eccentric mass.
Have fun.
awright