This works now with an iPad Pro 10.5" (might also work with an iPad Air 2nd gen).
It is a tight fit (especially if you try to slide it on on the camera side) but it shouldn't lose in the car.
I recreated it as an one part print (you need supports, see screenshots or gcode file).
It is also printable on the Prusa Mini (if positioned correctly).
The GCode File is created for input shaper (last 5.x firmware).
I used PETG and 15% infill but if your kid is a little active you should probably make it more durable.
The author remixed this model.
Recreation of the design from WojtekM for iPadPro 10,5" and created as one part (for stability reasons)
The original design was for standard iPads, but bend when used with the 10.5inch iPad Pro. Also the two part design always split due to the stress on the parts.