There are several references to Hall's being used by civilians, but the most interesting evidence is the number of them dug up during excavations in San Francisco in the past 20 years or so. When they've started construction on new buildings on what used to be part of San Francisco Bay before the Gold Rush, it isn't at all uncommon to uncover old ships that were being used as either storage or even shops during the early days when A.) ships were cheap (usually abandoned by the crews as soon as they hit SF) and B.) buildings were rare. At any rate, one of the ships which was excavated contained a large number of Hall's carbines, or rather the remains of them, since the ship burned during one of SF's periodic fires of the period. Anyway, good hard evidence of their availability in California in the very early 1850's.
As far as repro's go, Bill Laybourne of Ordnance Park made up a few dozen of them in the mid-1980's, but he's passed away long since. I had one of the first one's (#0013), and it was a fine shooter, with all of the major parts interchanging with my original. He used the Harper's Ferry-made M1842 as the pattern, complete with brass bands and buttplate. Sadly I traded it off to a friend, who later donated it to Ft. Gibson State Park in Oklahoma, where I assume it still lives. I have a photo of my compadres and I shooting off our Hall's carbines at night, BTW. LOTS of flame shooting out from the breech! It's pretty exciting, you might say.
Per the Rifle Shoppe parts, I wouldn't hold my breath. A friend has been waiting for more than five years for them to get around to casting the parts for the Hall he's been wanting to build, so unless you're real patient, I wouldn't bother with them.
Cheers!
Gordon