Thats insane. If it were me, I'd get the dimensions off of the old one then go to the
Donaldson Exhaust Catalog and get a part number.
I'd search that part number and I'd guess you'll probably end up somewhere like
Ryder Fleet Products where you'll see they're a lot less than $1000.
Another option would be to
just remove it all together. I know a few people who have done this and have been very happy with the results. I know on my Allis 7000 tractor I just run a straight pipe - mostly for looks, but it works well and sounds great. :B