Since they were pretty much part of Harrison's Brigade, might they have been represented under the Tensas Cav Flag by chance? I've looked for quite some time and can't find anything on it, except that the 2nd cavalry and Tensas have documented flags, though I've not been able to find a photo of either one. There is a Trans Mississippi flag with the reversed field in the top corner and the red and white bars, as far as I know that one is unidentified. Could that be it?