The Lever Action Rifle Company in Gresham, Or. had them listed in a catalog I have of his from 2000.
I don't know if he still has them. The last time I needed something from him( a flat hammer spring) he didn't carry it anymore.
His 2000 price for the repo Hepburn sight was $175 = postage.
503-665-9742, and at our August show he still had a few left. If you're thinking of buying one to use, save your money. The Hepburn sight gives a poor sight picture with either the peep or the notch.
If you want one because they're collectable, then get one by all means! Larry's sight is as good as the original, and an exact copy! If it wasn't maked LARC on the bottom, it would be impossible to tell from the original!
I have one in my sight collection, and an original on one of my Marlins, and LARC's is perfect. I've shot guns with both sights on them, and the standard buckhorn works better than the Hepburn notch, and a Marbles or Lyman peep works better than the Hepburn peep. It's just a bad location for the type of sight. The notch is too close, and the peep is too far away.