Ken,
After looking again at the Belle Bushnell fictional book based on the Pointe Coupee Artillery and their flag I noticed the following in her forward...

"It may be interesting to those who read this book to know that after changing the dates and mixing the names, I then tell of events that really took place, and not a few of the characters are persons whom in all truth I have known and now portray. But history tells of the brave fight made by the Point Coupee Artillerymen and of all Louisiana troops during the siege of Vicksburg, and of their gallantry throughout the entire war.

Though of the flag, their beautiful silken banner, few but the Point Coupee Troops ever knew that it was made by a sweet young gentlewoman, of strips from her own dainty gowns, and made for the one most dear to her; and proud indeed was the gallant young lover on that thirtieth day of May, 1861, and oh, so caressingly he held its rosewood staff, whilst leading the Battery Boys from New Orleans."

After seeing this I think it is safe to say their flag captured at Island No. 10 was made form a dress of one of the girlfriends that she mentions. Jack