Spare Flaps To Clip On

If you have access to a simple, off-the-shelf 3D printer, you can make replacement flaps from flexible material that can simply be clipped onto the existing shaft as needed.

Because of their flexibility, they produce or transmit less annoying noise than the usual welded-in metal flaps. I used the following filament for these flaps:
   BASF Ultrafuse TPC 45D

 Clamp flaps from 2:12 video time