Custer's division certainly did not attack MG. Lomax's division, they attacked BG/MG Rosser's cavalry division.
BG. Bradley Tyler Johnson's cavalry Brigade had: 8th VA Cav, 21st VA Cav, 22nd VA Cav, 34th VA Cav Bn, 36th VA Cav Bn and 37th Va Cav Bn.
Colonel William L. Jackson's Cavalry Brigade (BG. Henry B. Davidson's) had: 19th VA Cav, 20th VA Cav, 46th VA Cav Bn and 47th VA Cav Bn. (The 1st MD Cav Bn and 2nd MD Cav Bn, did not join the brigade till 19 October, 1864) Thus, they were not at the battle.
The 21st VA Cav, was in BG. Johnson's cavalry brigade in October, 1864. Source: OR 43, Part 1, Page 566, ibid, Part 2, page 903 and ibid, page 914.
Interesting enough, Jeffery Wert and Eric Wittenburg both have in their books, the 34th VA Cavalry Battalion lost their flag. Most likely their source was from the Official records. Edward Longacre in his book, "Lincoln's Cavalrymen: A History of the mounted forces of the Army of the Potomac." He does not have who lost the flag, but did write, "At least one battle flag."
When I came across this subject, I searched on "Google Books" for any help and little turned up. My sources on any Confederate order of battle will be from "F. Ray Sibley, Jr." "The Confederate Order of Battle" "The Army of Northern Virginia". That is a outstanding book, that I have with me all the time.
Have a good day,