Need help

I am looking for a material which can help in my product for visually handicapped.
Actulally it’s a product to teach gepmetric shapes and alphabets to the people with low vision or totally blind.
The product will be a base with some material (which i’m looking for ) on which if I move a magnetic stylus it will make a protrusion or opposite ( actually a surface difference)
So they can feel the surface difference using their fingures and can learn the shape or the alphabets whichever is drawn by the teacher.

Can anybody help me in finding any material which can help in this.
I have made a similar product using plasticin, ( for disabled)but i’m still working on it.
Your valuable feedback will be appreaciated.