There are numerous places on the net that you can purchase truck exhaust parts from, elbows, straights, u-bends, clamps, mufflers and a whole lot more. Depending on your skill level, desire, ability to do the work, area to do it and some basic tools, you can replace that section with new parts for real reasonable cost.
I just replaced my junk Aero 50/50 XL Stainless muffler with a new really quiet one from Donaldson muffler. The muffler cost me a whopping $75 and the one 5" clamp, about $15 more. So, I saved a considerable amount by doing it myself. It was not hard at all.
Scott