I don't think they are made by any aftermarket company BUT I believe that you can use clutches from other applications and can cut the "ears" to fit like the originals. The main issue is making sure that if you use "other" clutches that they would have to be equal in thickness when "stacked" as the clutch pack to the original clutch pack. There are certainly other clutch pack kits that have the same dimension as these clutches regarding diameter and inner diameter. I think many Eatons are the same size. All the clutches do is grip each other and the "steels" that are in between.
I think someone who has plenty of spare parts from different brands of carriers and axles could mix, match and modify to get something to work, actually there is no doubt in my mind that it could be done
