Maybe I'm not the right researcher to find this answer for you, but you have done so much for me over the years that I took a crack at finding this answer for you. I didn't nail this one, but I put together some pieces that may point the way for the definitive answer you seek.

I searched Frederick Dyer's "Compendium" in the unit histories section, series 1 and volume 3 of the "O.R.," (which was no help at all) the MO Adj General's Report for 1865, and then the online military service records in the MO Secretary of State's Missouri State Archives for the following:

I saw a mention that Henry P. Hawkins independent company came from Wayne County and the surrounding counties, but I bet you already knew that.

The MO Adj General's annual report didn't tell me exactly which companies in the 6th MO Cavalry (US) Hawkins' men went into, but it did tell me that the original companies that were mustered out at the end of their term in December 1864 and January 1865 were Companies B, C, F, G, H, I , and K. So, I concentrated on those companies starting with the original officers and then some of the original 1861 and early 1862 enlisted guys' places of enlistment. (I was startled to see that a number of the original company-grade officers resigned in early 1863, but I don't know the reason.) A huge number of the records I looked up in the online military service records showed these men enlisted in Rolla, but it appears the 6th MO Cavalry was organized at Rolla, so that doesn't always tell me where those men came from. It is possible that some of the men actually came from Rolla and the immediate area, but I could be wrong. Below is the breakdown for those companies I listed above and these include at least two of the original officers and two or three of the original enlisted men in each one:
Company B: Stone County and Rolla
Company C: Georgetown in Pettis County and Rolla
Company F: Butler, Madison, and Wayne Counties (This is my best bet for Hawkins' original company.)
Company G: Rolla (about five entries)
Company H: Pulaski and Miller Counties and Rolla
Company I: Rolla (about five entries)
Company K: Rolla (about five entries)

The only thing that bothers me about the above method is this 14 February 1862 statement in the MO Adj General's office report for the origins of the 6th Missour Cavalry:
"The battalions of cavalry known as [Clark] Wright's, and [Samuel N.] Wood's battalions, and Captain Henry P.Hawkins' company are hereby consolidated and designated the 6th Regiment of Cavalry, Missouri Volunteers...The colonels of the regiments named above will immediately distribute parts of companies and unassigned recruits attached to their commands, among the organized companies of their respective regiments..."
This could mean that Captain Hawkins had to spread his men out among two or three companies, but, of course, that would play havoc with the unit integrity that his company had developed in several months of campaigning. I personally doubt that he had to do that, but it is a possibility.

I realize this didn't exactly knock the ball out of the park, but perhaps it helps you some.

Bruce Nichols