The material you are describing is known as expanded metal, The sheet of metal is streched to make geometric shapes, usually diamonds. However expanded aluminum is very soft and may sag even with bracing. If you are looking to replace the top with something other than glass you might consider steel expanded metal (which is stronger). To hold the top in place you can make some small clips that can be welded or screwed under the aluminum rim of the table out of sight. Then prime and paint the top to match the table frame with a good quality exterior metal paint.

Thanks so much benco. That sounds like a great solution.

You can also get expanded metal that has been powder-coated, or can have it cut to size and then get it powder-coated. That would be the best for weather resistance.

A large national dealer in these products is the McNichols Corporation. Google them and see if there's one anywhere near you.

I suspect it will turn out to be cheaper to get a new table, or to have a glass shop cut a new piece of tempered glass.