I think you're in for a bit of a shocker when you see the price tag for "down-sizing" to either of those dimensions. In short, they aren't a size any retail outlet maintains at any given point and would have to be ordered through their distributor. You can call, but I doubt even TPP keeps either on the floor.
Much like when you go to Home Depot and look at the stock windows and doors, then ask about something in a different color or different jamb size, your jaw just drops since it becomes a custom order. If money is an issue, I strongly recommend replacing the brace. A good LFS can order one for you. Wait for the PETCO sale to come around again (July?). Or, if you drain the tank half way and clamp the brace so the gap closes and just crazy-glue a small piece of acrylic over the crack you'll be fine. About an inch either side of the crack is all it takes. I've had one on the brace of a 90G for about 6 years now.
Much like when you go to Home Depot and look at the stock windows and doors, then ask about something in a different color or different jamb size, your jaw just drops since it becomes a custom order. If money is an issue, I strongly recommend replacing the brace. A good LFS can order one for you. Wait for the PETCO sale to come around again (July?). Or, if you drain the tank half way and clamp the brace so the gap closes and just crazy-glue a small piece of acrylic over the crack you'll be fine. About an inch either side of the crack is all it takes. I've had one on the brace of a 90G for about 6 years now.