Picked up the last 4 lechuza pots in our local hardware store since they were on clearance.
We noticed one of the inserts was missing when we got home so i tried to replicate it the best i could.
The cutout for the water tube isnt the best but good enough to fit. 
Made my girlfriend happy and maybe it's gonna be useful for some of you. 

Printed it with 0,2mm layer height since i was to lazy to change my default profile.
Should be easily printable with bigger nozzles or just a bigger layer height.
Does not need to be pretty since its a functional print covered by dirt. 
Used 15% infill and 3 walls. 
Also turned on supports since orca wouldnt print it without, seems to be a flaw in the design but i couldnt be asked to fix that for like 10g of filament savings.

Takes about 150g of filament and 8-9 hours to print with my settings but can be brought down massively i think. 

If it helped you please leave a comment :)