Due to aging plastics and design, these sign indicators mount tab would snap right around the support structure begins closer to the housing. I've fashioned the new mounting piece that sandwiches the remaining plastic snug and is easily printable with no support. Once fitted, you should be able to bolt the housing back on. The direction it's printed should allow for strong structural rigidity.
I've printed this part using PETG, 65% grid infill, with 3 wall loops on a Bambu X1C. Install is not difficult, you should be able to super glue the piece using glue that has more viscosity and takes more time to set, then use some strong tape to secure the piece as a secondary (Flex or Gorilla tape perhaps). Mount hole plastic is m4 self tapping screws.
I have not tried to use this on left (RHD passenger side) indicator yet, but this should fit but just flipping the piece over. I will work on that side in the near future.
The author marked this model as their own original creation.