It's my understanding that the "wing style" knob is NLA from Eastman but perhaps you already know that. Maybe a member will have a used one available in orange. The earlier ones were red. e-Bay is also an option but usually the entire control is sold with the knob.
The control itself has a friction disc that acts as a brake to keep the throttle lever from moving on its own. Some controls were held together with a rivet and some had a nut/bolt. The latter can be tightened with wrenches. The former can be tightened by clamping vice-grips on the rivet and squeezing. OR.... you can remove the control and tap the rivet with hammer blows of increasing force to get the rivet to tighten up. Just don't overdo it. Another solution is to replace the rivet with a nut and bolt. This is a common problem with the throttle lever and all of the above solutions have been used by owners in the past with good success. Pick your poison.
The control itself has a friction disc that acts as a brake to keep the throttle lever from moving on its own. Some controls were held together with a rivet and some had a nut/bolt. The latter can be tightened with wrenches. The former can be tightened by clamping vice-grips on the rivet and squeezing. OR.... you can remove the control and tap the rivet with hammer blows of increasing force to get the rivet to tighten up. Just don't overdo it. Another solution is to replace the rivet with a nut and bolt. This is a common problem with the throttle lever and all of the above solutions have been used by owners in the past with good success. Pick your poison.