I don't think there are any Dirt Devil U HEPA Cloth bags made. But, the hole size and the dimensions of the bag are close enough to a Hoover Y HEPA Cloth bag that one of them should work.
Also, for the Dirt Devil Featherlite uprights requiring the D bag, I was able to make a Kenmore 5068/Panasonic U HEPA Cloth bag work by making the bag collar hole slightly larger. Also, a Royal B bag or the Perfect Upright HEPA Cloth bags used in their Sanitaire knockoff should also work, the hole size should be nearly identical to the Dirt Devil D bag.