Stabilizer rubbers and front axle crossbars

Hello, V8 community.

For the TÜV now in August I must probably or badly carry out a repair.

My vibrates / shakes between 160 and 180 km/h, and when braking anyway.

New brake discs and pads have been on it for 8 000 km, so the reason can't be.

Steering damper is new since 15 000 km, it can not be.

After 287 000 km, however, the front axle suspension is certainly knocked out.

That's why I'm here.

1. Switching the front handlebars - should be no problem.
2. Change stabilizer rubbers - Problem: 26 mm rubbers are no longer available according to ETOS.

my questions:

a) Which parts do I need for repair?

b) do I need a 28 mm stabilizer and the associated rubbers or do I get the 26 rubbers for my 26 mm stabilizer somewhere else ?

I would be very grateful for help and encouragement.

P.S.: I used the search function and already read something.