Shipmate, the civilians around here might not be famaliar with this the same way a Bluejacket like you and a Leatherneck like me are familiar with it, but the sea services consider "duffel bag" to be an Army term. The Navy, Coast Guard and Marine Corps refer to it as a seabag. Among many other items, I still have two pieces of gear that were issued to me that first night at boot camp decades ago: one pair of boondockers (combat boots) and my seabag, the old single strap type, not the backpack type. So to answer your Q as to do I own one, I sound off with a hearty, "Yes, sir!"
The only duffel bag I ever owned was issued to me by the US Air Force. I escaped 51 years ago and I discarded everything that reminded me of that sordid period of my life. The reputation of the US military was so lousy that some Americans were refusing to pay taxes. And it still took another fifteen years to get out of that war.
Randy D 