I see this MT9M111I99STC and several other Micron models are available through DigiKey and I presume you have contacted them. What's the story, can't they order the Micron for you? Can you live with lower resolution as they seem to be in stock? Digikey has been very good about ordering non-stock items for me before, so should be able to help you out, albiet with a significant delay perhaps.
A student usually is stuck with finding something at a Distributor. This includes Arrow, Avnet, Digikey, Mouser and lots of other smaller companies. The pros usually deal with a Manufacturer's Representative who is typically a salesman with a Technical Sales company contracted to represent the manufacturer. The Rep has technical knowledge but doesn't stock anything, and can get you parts directly from the manufacturer.
The biggest markets for image sensors include cellphones and cameras and it is not unusual for a company that is going after these big markets to ignore the little guys and the students. This is especially true when the type of parts usually require technical support. They only want to support the biggest accounts. So trying to deal directly with them or the Representative is often a waste of time. That's one reason why we have distributors to help out the smaller guys. This isn't true of all parts, just the ones that are really hot in cellphones right now.