L & R's Ashmore lock will work, but as usual it wants some tweeking. You can replace their roller frizzen spring with their Small Manton frizzen spring, and split the boss on the frizzen and install a roller bearing.
To really improve the lock for the purposes of a Hawken rifle, the plate should be filed flat. In other words, remove the edge bevel. But that's certainly a taste thing. And of course, you willhave to engrave the plate "Ashmore Warranted".
Here's that lock in a rifle I made a few years back...