If anyone has a 577 you'll know the left/right switch on the 177 text fixture has a tendency to be broken off. The NOS switch is pretty much unobtainable but it is possible to effect a repair.
The switch is a Switchcraft 41000 series with 4 sets of contacts. This switch has contacts which are attached with screws onto an actuator body. The details of the body determine if it is an On-Off-On (3 position), On-On (2 position) and locking or non-locking. The one in the 177 is a 3 position locking switch.
The correct actuator body can currently be obtained from the Vintage TekMuseum.
If you cannot source it from them, you can get a Switchcraft 41312L or 41324L, strip off the contacts and have the correct part.
However, the toggle (the part that breaks) is common to the entire 41000 line so you can get the part from ANY 41000 series switch, 2 or 3 position, locking or nonlocking and fix the original actuator. I found one on ebay under "USA made Switchcraft Toggle 1P1T Momentary Tele-Paddle PTT Switch" for under $6 US shipped. The actuator shape is unique to the 41000 line so it's not too hard to identify one once you know what to look for.
Use a small pin punch and drive out the pin in the barrel holding the toggle in place. Be careful since there's a spring between the toggle and the rocker in the body. I'd do this to the new part first so you can get an idea of how the switch is put together. I used a filed down finishing nail as a punch.
Take the actuator out of the 177 fixture. Remove the looping compensation variable capacitor by unsoldering the rear wire, then removing the knob and nut. You may have to unsolder a couple of the wires on the switch to get it out. Bend it back and unscrew the switch contacts to remove the actuator. Leave the screws in the contacts so none of the spacers fall out. Do not joggle it.
Punch out the pin holding the broken toggle. When the pin is almost out you should be able to pull it the rest of the way with pliers (it helps to hold the actuator upright when doing this). Hold the toggle so it doesn't shoot out. Insert the new toggle and spring, put in the pin and tap it home. You want the head of the pin just below the threads so the nut spins down.
If you do this carefully you won't disturb any other parts of the actuator mechanism. There are 2 tiny wheels, two tiny axles and a rocker in there that could fall out if you're not careful. If they do fall out, put them back in. They only fit one way.
Check the action. It should work like a new switch.
Reassemble. Be careful to get the contacts aligned correctly. You want to have the paddle off the switch before trying to get it back in the fixture.
I've attached a picture of the repaired actuator with the old broken toggle and spring.
Reassembly is left as an exercise for the student
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