This is a very easy print.  I used a 0.8 nozzle and PLA but I am unsure how long this will last in the sunlight. I will not be surprised if I have to find a filament better suited for outdoors later.

I am in the USA and this cover fits snugly to the black corrugated drain tube that you will find at stores such as Home Depot, Menards and likely your local hardware stores and home/garden centers.

I created this in Onshape and it is public.

https://cad.onshape.com/documents/f455a052c79e49a016a4dac7/w/6fddf0746ceb6f2def6a2275/e/4449416804976d4b37988427?renderMode=2&uiState=63274da2eedf8a2752228718