Glass Fireplace Screen

You can't use ordinary glass. Finding someone who will make up the glass you want, is possible, but it may be more expensive than you think. The whole project may well cost you more than buying prefab doors. Your best bet in finding the glass is to check with a custom fireplace shop and ask them about getting just the glass. I would guess very few regular glass shops are going to have a source for the glass.

Fireplace glass is actually a high temp. high strength transparent ceramic, and takes special materials to make at the outset, and is not simply "tempered glass". Nevertheless, there are a number of fireplace and woodstove "glass" providers on the internet, which supply these ceramics.

If you are going to use the fireplace with the glass closed it needs to be ceramic. If the glass will be doors that are kept open when the fire is going it can be tempered glass. Obviously ceramic is the much better choice.