I think Paul Components makes some good mechanical disc brakes with IS mount. They are expensive, but probably work pretty well.
Edited to add: I agree with mstateglfr above. Some posters remind me of teens who act as if life would be impossible without cell phones. Those of us who remember the days before cell phones and hydro disc brakes know that neither is essential.
Last edited by Koyote; 12-22-18 at 08:40 AM.