I know Idaho is a big state, or at least a long state, so I don’t know how accessible Ponderay is to you. However, there is an outfit called Buffalo Arms in Ponderay that would be worth checking out. They specialize in black powder cartridge guns and equipment, but they also carry new and used muzzleloaders and everything you need to shoot them. I have no doubt they would be familiar with Hawkens. Google “buffalo arms blackpowder” to find their website. You can look at that to see if they might be worth a visit.
Also, October Country Muzzleloading is based in Hayden, Idaho. Again, I don’t know where that is in relation to you, but they are a full-service muzzleloading supplier, with new and used guns and supplies... The works. I can’t say that they have a Hawken for you to examine, but they might, and you can bet your hoss they know what one is. They also have a website. Google “October country black powder (I don’t know how to post links with this new device my wife made me buy).
You might also go to NMLRA.org and look up the Idaho field rep for the National Muzzleloading Rifle Association. He could certainly direct you to someone who might help.
Finally, there is a forum member named Joseph who had a somewhat non-standard Hawken-style rifle made by a small-town gunsmith in Idaho. I don’t remember the builder’s name, but the rifle was outstanding. If Joseph sees this, maybe he will tell us more.
Good luck!
Notchy Bob