I bought mine on ebay. I dont know if you need a one wire or four wire. but here are some links. None of the parts stores are going to stock this item they all have bosch. I have heard NGK makes good o2 sensors as well. I have never used one personally.

4 wire:
eBay Motors: o2 oxygen sensor HONDA CIVIC 92-00,DENSO 4 wires new (item 270027062011 end time Sep-15-06 01:35:41 PDT)

1 wire:
eBay Motors: DENSO O2 Oxygen Sensor Acura, Accord, Prelude Civic CRX (item 170029295595 end time Sep-23-06 16:36:47 PDT)

Hope that helps.