According to Wizbang http://www.whizbangcider.com/2012/08/test-2.html
He says the Insinkerator model 80s (which is no longer made) works well. For newer models, supposedly the 3/4 hp Badger model 15ss is built like the old Insinkerator model. Also the Kenmore 3/4hp disposal part no 60572 is supposed to be built like the Badger 15ss.
As an aside I’m not sure it’s necessary to buy the books from Wizbang. Building an apple grinder out of a disposal was discussed extensively on the old fruit forum. Don Yellman (Jellyman on the old fruit forum) was the first (that I know of) to come forth with this idea (first discussed on an older forum called Nafex). I recall he was really pissed someone took his idea (that he freely shared) and put it in a book to sell for money, without giving him any credit for it.
From past discussions, the big problem with disposal grinders was that they would overheat and kick out if used continuously. Another problem that some people complained of is that they would grind apples a bit too fine, so that that apple juice was cloudy. Some purchased grinders (not the disposal type) would grind apples a bit coarser so that the juice was clearer. Also the consensus was that purchased apple hand grinders didn’t work very good at all.