Well, netbooks are out of fashion now. Sony Vaio did a good one not so long ago. The problem is they just weren't very portable. They were kinda thick, had poor battery life and fans and were comparatively expensive for what you got. They've stopped making most of them.
What I can recommend is a
Chromebook. They're small, cheaper devices made by Google and partners like Acer, that don't have all the features of a traditional computer. All the software is accessed by the internet through Google apps.
For example, with Google Drive, you have online storage where you can store all your documents, music, photos etc. You can access them from any computer with web access. Then you have google apps for word processing, power point and spreadsheets. They have great battery life, too.
I checked and they do have text-to-speech software, as well as voice dictation and other accessibility features. You can also use some simple parental control tools as well.
The cheapest one appears to be an
Acer C720. Looks quite fancy, actually.