The sleeve nut would be relatively easy to make. Start with 4140 hex stock, drill and tap the ID threads, turn down most of the outside to a proper sized diameter to leave a hex head on the top and heat treat to ~35 HRC (the last part I could take care of, I know some folks...). On a bar stock feeder, this would be easy to make. Wish I had one of those.
There is a place in Juneau that specializes items such as this, I will make a model and send it to them. The challenge these days is that machine shops are so busy.