They are available, but not cheap. If you are, or know a machinist, you might build one, as they aren't too complicated. We thought about building one, but the owner of the
B6000 decided to go another way. He re-engineered a mower that I had to work in reverse. All it took was changing the idler pullies so they would keep the belts tight going the opposite way, and putting new blades on it, that cut in the opposite direction. He is pretty handy but he did all that in one afternoon. The blades he found for the finish mower were 1/2" shorter than the originals, but they don't leave a gap as they cut, so that is the main thing.
He looked at a couple of the old bush hogs I have and considered putting reverse cutting blades on them. The finish mower does the cutting he needs so he didn't do the bush hog, although it would probably be easier than the finish mower.
What other attachments do you want to be able to use?
David from jax