Toilet seat with integrated child seat

Hi, this is my first post on here, so hopefully it`s ok. 

I am looking for a toilet seat within an integrated child seat. The problem is, it seems our toilets are not a standard shape, they seems to be a square (or technically `eckige`) shape, and I can`t seem to find an integrated seat that fits that. I wondered if anyone had come across one like this? Or has any recommendations of where I can look. I`ve pretty much exhausted the google searches.

Thanks in advance if anyone can help.