Plug rear cables Tero 4.0

I just took off all the fenders/lights from my tero 4.0, now not EQ anymore :).

There is a hole now where the cables ran through. I'm trying to find a plug that would fit that to prevent water/dust from entering, but I can't find it anywhere it seems.

Anyone know what kind of plug I need? The outer area is approx. 2.4cm W x 1.4 cm H.