Lazydays in Tampa sells Forest River and has a large repair shop. You might want to give them a call and maybe they can point you in the right direction.
Go to any RV repair shope where they are replacing hardtop roofs everyday and ask if you can remove the 4 corners on a discarded roof yourself. I did that in my hardtop days and they didn't charge anything.
I just ordered new corner moldings from forest river for my model 822 1998 flagstaff popup. $4.56 each plus ship. You need vin # model etc. Phone for parts 574.262.2212