445 universal

I'm not sure from your description what is missing so I will describe what was originally supposed to be on the throttle lever.

Where the throttle comes through the dash, there is a hard steel bushing with a tapered hole in it.
A nylon bushing that fits into the above bushing is held to the throttle shaft with a small (I think 1/16") roll pin. On the throttle shaft, below the dash and bushings, there is a spring that won't fit through the hole in the steel bushing, then a washer. The spring is somewhat compressed and held there with anothe roll pin under the washer. This the friction between the nylon and the steel bushings is what holds the throttle in position when you mopve it. Near the lower end of the throttle shaft, there is a lever that is held to the throttle shaft by another roll pin. The throttle linkage from the governor connects to the other end of this lever. Finally, at the bottom of the throttle shaft, there is a bracket that the throttle shaft just sticks through & is mounted with one of the bolts that holds the steering column in place.

A common problem with the throttles on these tractors is that the roll pins break. Sometimes they are a bear to get out. Heating the pins or pieces of pinsd red & letting them cool usually makes it easier to get them out.

John