Toyota has made both kinds: the one-way, and the two-way. They are both Toyota parts.
The one way is threaded and screws into the diff.
The two way has a simple hose barb, and is intended to be placed at the end of a hose.
I don't have the part number for the two-way one in front of me, but right now I've got both types in my spare parts box.
The one that came on my '97 3rd gen, as well as the ones that came on my 4WD '91 truck, and two Land Cruiser FJ 60's, were the one way type.
Additionally, the one way is all metal(except for the rubber flap inside), while the two-way has a plastic body with a metal cap.
I got underneath there and put onto the locker breather a piece of gorilla tape and 3 or 4 pieces of electric tape to close it up. I feel pretty comfortable with that for a quick trip to the desert, assuming I will have to make a few stream fording.