The only viable alternatives i have heard of to glass are a lot more expensive, ie. exotic ceramics.
A mirror substrate is a just a support structure for a thin layer of aluminium but the stability and accuracy required means that few materials make the grade. Rest assured that if cheaper materials could be used to create the required optical surface, the Chinese would be using them in mass produced scopes
You could probably fashion a shaving mirror from many materials but for illustrative purposed consider these numbers.
A mirror with 1/4 wavelength surface accuracy is considered fairly poor for a telescope mirror. A 1/4 wavelength of green light is around 125nm. In laymans terms thats 0.000125mm deviation from a perfect parabola across the face of the mirror.