In the US this would be a good deal. Tanks over 75 are hard to find used, and new are crazy expensive because the chain stores sell them as kits with everything rather than the tank by itself. (Petsmart has a 125 with stand for $750.) I would inspect it and make sure the glass can be cleaned enough for your liking, you can't buff out badly scratched or hazed glass and older tanks are often in rough shape.
While having bracing is important, I'm not sure it's as important for these larger tanks. You'd be using the same depth of substrate as a smaller tank, which means there's less weight and pressure being put on the glass of a bigger tank. That looks like at least 1/2 inch glass, so you shouldn't get much bowing. If it was full of water and weighed 1100 pounds sure those braces are vital, but you'd be lucky to make it to a quarter of that in substrate. You can definitely buy replacement braces though! Just a quick Google brought this up, and once you have exact measurements you can probably find more options. The old one should pop with a little work because of the age, then it's just cleaning with a razor blade and fitting the new one with silicone.
https://aquariumframeswholesale.com/custom-frames