Repairs Craftsman riding mover frame broken

The frame on my '96 Craftsman 50" riding mower had cracks develop in the frame several years ago. They are about midway between where the engine mounts on both frame rails. They started as small hairline cracks and grew slowly over time. I hadn't looked at them for over a year but I after noticing the mower was mowing lower than usual yesterday. No matter how much I tried to adjust the mowing height, it was still cutting low. I thought maybe something was broken in the raising mechanism so when I looked, much to my horror, I found the problem. The frame was completely broken on both sides. It looks like to the only thing keeping my front end attached is the engine. If I keep using it this way there's probably a good chance I'll bust the engine mounts of the engine. I don't have a welder that I could weld the frame back together so I am thinking to bolt some rectangular thick gauge flat stock steel on both side of the frame to reconnect the two parts. The problem is where can get some steel like that?
Has anyone else had an issue with their frames cracking on any riding tractor? It has a 25hp Kohler Command engine. Could just the weight of the engine caused it? I'm not a heavy man. I barely weigh 190 lbs.

I see multiple steel suppliers in Washington to visit and they may cut you a couple of steel plates from what they may call strap. Three 1/4" fine thread bolts on each side of the crack with the center bolt off set from alignment of the other two. For a vibrating lawn tractor I recommend Nyloc Nuts with 2 flat washers / bolt.

That's the plan if I can find a steel yard close to me. Three bolts are better than the two bolts on both sides I was planning. I always use lock washers but Nylocs would work well too.