This will either be great or just plain stupid… I’ll let you try it and see.
Cook it up in a covered pan in the oven. It doesn’t have to be completely cooked since you were using raw anyway, just enough to stiffen it up. Dump the sausage in either a food processor (smaller batch) and pulse it a few times. You may end up with very small chunks or pellets if you do it too much (or you may not get enough break-up if you don’t do it enough). I’ve done it once, and I had to go to the fine pellet version. It’s not bad if the people ordering it actually LIKE sausage, but if they’re planning to pick it off, it ain’t happening. The second choice would be to break it up by hand some, then put it in the mixer with the flat beater and let the mixer break it up into smaller chunks. Again, no guarantee of greatness here.
Another option would be to get it in patty form, cook it, and then cut it by hand into quarters or such.