That would depend on what you have to work with. Some light steel and I would build a metal brace with two small peices attached on the sides with a longer piece welded across them at a 45. Drill two holes in the longer piece and attach to the leg. No welder then I would cut a 4x4 section with a jigsaw to match what I described above and reinforce with large washers or some square steel plate. It wont be as strong but It would work just fine.
Edit: Or after reading below I would order those brackets from amazon.
