Sorry!
I feared some confusion on this issue, which is why I wanted to check "Tennesseans in the War" last night, but -- well, you know the rest of that story. The NARA microfilm index shows two cavalry commands from Tennessee called Newsom's, one numbered 18th and one simply called Newsom's, reels 65-66 & 83. I may have been thinking about Nixon's Regiment, not Newsom's, which was raised in the Tennessee Valley during the late spring and early summer.
There are a few stray references to Newman's Cavalry on the web. Here are a few, which should be searched for the name "Newman":
http://www.mach500.net/liggetkw/incw/prisoners/indy/confed-qr.htm
http://www.geocities.com/~cindycasey/civrostr.htm
Probably the entry that is most meaningful to this search will be found here. The line in question mentions "Newman's company, encamped near Portersville, De Kalb County, Ala." This company appears to be part of Col. Lowe's (13th) Alabama Cavalry Regiment: