A larger piece of glass? Just kidding... I'm sure you already thought of that.

What about cutting a piece of plywood to the size you want, then covering with a tablecloth? It might be just as expensive as buying a larger piece of glass, though.

But with a piece of ply wood you can gold it, using piano hinges and get a really big table....you could even make it oval.
I have a folding table top that makes a 36 inch card table into a 50 inch round table.