Sorry to hear of your tire problems. One reason most of us have been changing tires every 4-5 years is to avoid the collateral damage that a steel belt whipping around at 700 rpm can do. Mission tires have not had a great reputation, but a number of members, including me, have gotten good service from them. An 8 year old trailer should really be ready for its 3rd set of tires by now--regardless of mileage--because rubber dries out, ages, becomes less flexible and eventually blows up.
I don't know your travel style, but am guessing it's not high mileage. They're still Chinese, but I would take my chances with Goodyear Marathon
sooner than some of the odd ball names sold by most RV dealers--all still made in China.
I'm not sure whether it's the fender skirt or wheel well that's broken. Icon
has already made some fender skirts for other members and if they don't have your mold can make one if you send them enough big pieces/measure the good side... call them to see what they have/need.
If it's the wheel well... Icon does not show any on its web site, but might be able to make one--again, if you can send them the pieces. Do a Google search on "rv wheel well replacement" to see all kinds of links to rv forums where others share your experience and are looking for help. I'm not aware of anyone else on SOC that has replaced a wheel well. If it's not damaged too badly, rebuilding it with a fiberglass body kit could be another option.