How to locate the generic Bosch O2 sensor?

[Zsolt]

I am having a heck of a time finding a generic 3 wire O2 sensor for my
car. Every single place I called only comes back with the OEM part, and
can't seem to be able cross reference the generic Bosch.

I am looking for 2 of them, one is for an 88 5ktq, the other is for a 90
V8q.
Any suggestions? Part number, or perhaps a different car make model I
should look for that will bring it up?

Thanks,
  Zsolt