I wonder if they are fitted by Knaus rather than being a standard Renault part?
It's an 06 plate. i think you may be right about them being manufactured by Knaus, and I wonder whether they're actually necessary for any legal reason?
The Sun Ti has a fairly wide body, so mounting the side repeatersd on these stalks does make them slightly more visible (and vulnerable). I'm sure the mounting hole is a standard, so I may just replace them with the flush-fitting side repeaters.
Our van is based on a Renault Master, built in 2007, and of the "newer" post-mid-2006 front end style like yours. We have the extenders like you and they are a Renault part - the OE part referred to above looks as though it will fit though. Note - you would also need that additional part they show for the inside if that is broken/missing.
PS - The best pic of the front of our van can be seen on the Ledcom website. The extenders can just be seen. [This is our actual van in the pic]
No longer motorhoming due to illness, but always prepared to help by sharing any experience I may have.