This summer on the ferry, one of the turn signals on my KTM 990 Adventure R broke. Initially, I tried to glue it, but it only lasted a few days. Convinced I wanted to replace it, I checked the cost of an original turn signal (only €35 actually) and wondered if I could make one myself.
Why choose the originals again? They are optimized for off-road and even in case of a fall, they don't break but detach.

Let's go step by step:
1) Unscrew the turn signal and disconnect the connector.
2) Unscrew the clear lens.
3) The reflector should be pulled out towards you. The interlocking mechanism is visible in the photos.
4) Disconnect the connectors attached to the reflector.
5) Break apart the stem of the turn signal to reuse the original bolt.
6) Find a way to clean the old bolt as thoroughly as possible (I burned it to melt away all the plastic still attached).
7) PRINT YOUR NEW TURN SIGNAL. I made mine in TPU to make it even more suitable for off-road, we'll see how long it lasts.
8) Thread the wires inside the new stem.
9) Glue the bolt into its seat with simple super glue and proceed in reverse for assembly.

Compared to the original, the fastening pin is missing, but you can overcome this by inserting a short screw. I preferred to do it this way to improve print quality.
When printing vertically, supports were only needed for the bolt part.

EDIT: After several enduro rides, and at least 3000km covered, the turn signals work great even above the hot exhaust!