I saw this topic before, good work. The whole unit can be bought from Poptop.nl but it costs a whopping €50.
I'm thinking about replacing the tail lights also.
If you mean the internal LEDs then the club shop has replacement bulbs which are a straight swap. However I found the blue "daylight" light from these to be too cold at night. I found these slightly warmer ones which are better, though I still miss the warmth of the original bulbs... https://m.miniinthebox.com/product_...m_medium=newsletter&utm_campaign=MITB20170406
This is for a T5. Not sure if it applies to T4 but presumably it does, if the bulbs are the two-line kind. Excludes bulb above the hobs.