Acrylic is real easy to work with. I go to Industrial plastics and check out their 'off-cuts' bin for appropriate sizes and its discounted 30% from the regular $6/sqft. They have even given me free small pieces (1"x4ft) for odd jobs.
Acrylic Weld-on is the glue I preffer as its thicker than the other stuff (can't remember the chemical).
Just get a piece that's long enough to overlap the front and back of the top where the brace was. 1" overlap should be more than enough. Clean the top well, glue it and that's it.