Buying IR sensors

Where can we buy new IR sensors? All of ours seem to have magically broken over night in a way reminiscent of Titanic.

From the FAQ:

Q: I can’t find the TSOP34840 sensor in stock anywhere. Is there an alternative device?
A: Yes, use the virtually identical Vishay TSOP4840, which is available at Mouser and Newark (where for some strange reason it’s incorrectly listed as a resistor).