You may find that new ones do not last as long as a lot seem to be more cheaply made than they used to.. say Oceanic in the 90s and early 2000s
I've personally seen far more failures on $/gallon tanks than I have from older used ones.
if you aren't worried about the looks, you can go to home depot or whatever hardware store, and get a couple of angled pieces, and connect those with screws or welding or whatver to the correct length.
I tried fixing it and failed. I used jb weld 50112.
This is what I did. The brace had a piece that was cracked. (red line in picture. the red circle is a pressure point where the broken piece and frame joined). I broke it off and started with epoxy to bond it to the glass and plastic rim. I spent 30 minutes of pressing and using a clamp to get it to stay. Finally it held without me holding it. I let this part cure for 30 hours before starting the next part. I put the epoxy on almost every surface. Under the plastic piece. On top of it to cover the seam/crack. Underneath it where it meets the glass.
Saturday night I used a bar clamp to bring the glass to its original place. Again I put the epoxy on every surface and cracked part to connect the brace to the frame. I let it cure for a couple of hours. As I took of the clamp the brace and piece I fixed Friday started to come apart. I closed the clamp back and started putting epoxy everywhere again. Let it cure overnight. Same thing happened in the morning. Taking off the epoxy was easy. It peeled right off.
I think if I would cut a piece of glass to put under the brace and either bond it withe silicone or epoxy it would help reduce the pressure on the original brace. Then even a weak bond would keep the center brace in place and make it look presentable.
My question is if I cut glass with a glass cutter or the twine and fire method would it create a clean break that doesn't need sanding?
I am not surprised that happened; the glass doesn't bow out just like that. It is one thing to have it empty, imagine the pressure when filled?
Even fixed I would only use it as a terrarium. I agree with Doug just get a used one they just aren't worth much.