My AC contactor CR453CB3HBAAG went bad. But I can't find the same part online, even on GE's partstore.com web site. My AC is just five years old. Can someone help me to find replacement?

I have the same problem. Did you find the part?

A contactor is a contactor. You do not need to get a specific number as long as the operation is the same as well as the voltages. Most residential units use a 24 volt coil along with a 2 poles for power for 220/240 single phase electric. There are many of them on sale on Ebay and at many HVAC supply houses that will work. You need to also know the amp/current draw capacity also. Usually 25 or 30 or 35 or 40 amps. You can use a higher rate on a lower rate draw but not the other way around.

Honeywell Definite Purpose Contactor, DP2030A 1003 NNB! - eBay (item 300370650926 end time Dec-24-09 10:47:31 PST)

FURNAS 2 POLE 30 AMP 42BF15AJBBP 24V Coil CONTACTOR - eBay (item 350279799892 end time Dec-15-09 18:51:05 PST)

Most are either single-pole or double-pole. Find one that meets or exceeds current ratings of what you are replacing.