I've got one that is old and looks home machined from plans. It is not a Brock. I had it in N4ZX. Not bad but not a Brock. I;d have to scrounge up a spring. Back in those days they did not use the spring just a push rod. Scary! Anyway, it worked well. So if you are interested, let me know. I don't even know how much to charge for it.
Dana