I think there are only two basic types of O2 sensors; wide band and narrow band. Yours will be a narrow band and will be far more common and cheaper than any wideband. Narrow band are usually around $75, while a wide band starts around $200.
Now, that said, there are two kinds of narrow band O2 sensors; heated and unheated.
The heated ones have an additional wire. I don’t have, nor have I ever worked on an EFI scooter, but I would bet money that your O2 sensor is not the heated type.
So what you need is one with the same number of wires and hopefully the same connector. And the same thread size, I think there are two different sizes of that also.
I would try taking the old one to the part store and see if they can match it up. If they won’t, tell them to try one for a ’94 chevy pickup with a v6. That should be the same type sensor.