Bosch makes them and you can get them from an auto parts store cheaper than from the Dealer. There are two "O2 sensors" and they are different. One is a "fast" fuel ratio sensor, up front, and the other is a "slow" O2 sensor. You need to know which you need. They look the same except for the connectors are different.

I replaced both of mine and they still trip a code off road because they don't heat fast/strong enough. The one from the Dealer was $350 and a parts store was $160.

Lars,
Gold Coast Cruisers |My 4Runner