I am looking for robot constructor general plastic parts I do not know how call it, but I mean something like these pics:





Can I find something like this plastic parts in general or I must design them in solidworks and ordering for mold production by myself? 

My goal is to build some educational robot kits for kids by this parts.
The first picture is from Elector, 
 the second is kai robot.

They are both robotic kits from Iran, you can order kits from their site.

If you are looking for a Lego solution,
the Lego Eduction program has robotic kits like  Mindstorm and WeDo, or you could look at Lego Boost