The rubber serves as the spring. Back in the day there was an aftermarket booster spring that connected between the steering shaft and S wire and served two purposes. It helped make a good ground for more reliable honking and gave a bit of a boost to the horn button because the rubber alone sometimes sets the button level a tad low. I've not found anyone making them these days. I'm not familiar with the horn cup. My coupe doesn't have one. The holes that the S wire run through are in the steering wheel. Hopefully someone with intimate knowledge of that setup will come along shortly.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.