I have looked at the signal output from the sensor with my 'scope and I've also had a read of the datasheet. There is nothing I can see on the output from the receiver that is usable. My interpretation of the datasheet is that is definitely a go/no go output, the trigger level for this is set internally. There's nothing I can get from the datasheet that says that this trigger level is user adjustable.
If there is something that can be mass produced and is more reliable and robust than a small offcut of cardboard and sticky tape then I for one would be interested. What I have found is that the relative positions of the lock and pin hole are sensitive. Now, it may be that a different size hole would not require "setting up", but I haven't tried that myself.
's idea of shrink wrap is a good one, but not everyone has shrink wrap or the ability to shrink it safely. I've already destroyed one sensor whilst soldering on my test leads.
Not sure what the next step is, but happy to help/test... Mine is to get some fruit juice from the supermarket!