I bought an extension sun-visor for our VW Beetle which has ludicrously narrow factory-fitted visors – they don’t block out any sun at all when driving. This is the product I purchased :

https://www.amazon.co.uk/dp/B079M1ZHX8?ref_=pe_747761_41376721_dpLink

Unfortunately, the clamp on the extension device does not shrink down enough to attach to the existing visor. I was pretty sure that all similar products would have the same issue, so rather than send it back I decided to adapt it so that the distance between the clamping “claws” is reduced. Since other people may wish to attempt this, I am posting the instructions for the project.

(Safety! This is a medium difficulty hack – to undertake it, you should be confident working with precision tools and small parts.)

To carry out this project you will need :

1. Pencil and ruler.
2. A vice/clamps/workbench to hold things safely while you cut/drill.
3. Protective goggles for your eyes.
4. A cross-head screwdriver.
5. A cutting tool (rotary or small hacksaw).
6. A drill.
7. A pilot-hole drill-bit.
8. A 16 mm drill-bit.
9. Some sandpaper and sanding block.

(Safety! – If using power tools on plastic, use eye protection and do it in a well ventilated room. https://vividlearningsystems.com/blog/30-tips-for-hand-and-power-tool-safety)

Here are the steps :