It appears to me that the most often mentioned builders of top-quality Hawken-style rifles are Bob Browner, Brant Selb, and John Bergmann. There are certainly other people building them, but I don't remember all of the names. As an example, a forum member last year showed a splendid .58 caliber Hawken that was built by a little-known maker in Idaho named Robert Bradley. This rifle had an atypical "snail" and an unusual triggerguard (for a Hawken), but there was no mistaking the rifle's pedigree. Check out posts 61 and 67 in this thread:
Is That A Hawken?
A custom builder should be able to make a rifle in the style you want, but built to your specifications for length of pull, drop, caliber, etc. Expect the cost to start at about $2,000, and from there, the sky is the limit. My rifle from Mr. Bergmann took about eight months. As noted in previous posts, some of the other builders may not be able to deliver for 2- 4 years or more.
I have heard some very good reports regarding the Hawken Shop kit. I think the Hawken Shop can now offer completed rifles, although I don't know who their builders are, or the time frame, or the final cost. To my knowledge, this rifle is only available in .54, but it has an excellent barrel.
If you are not ready to take on the cost or wait time of a custom rifle, you still have some options, especially if you are willing to make some compromises. Pedersoli's Rocky Mountain Hawken will cost you around $1,500 in maple or $1,300 in walnut. It is in .54 caliber. You have said you want a .58, and I respect that, but this is a compromise to consider. These rifles are not authentic in every detail, but they are close.
Finally, I would suggest looking at used rifles. A forum buddy of mine just recently bought a fine .58 caliber Hawken-style rifle from the classifieds on this board. Check the classifieds every day. Also look in on used guns from Track of the Wolf and The Gun Works. You never know what might turn up.
Good luck to you!
Notchy Bob