I picked up a pair of Kriega KS40 travel bags some years ago, I think I got one pre-owned and bought the second new, expensive-yes but fantastic quality and these have the advantage of opening and packing like a small suitcase rather than the more common stuff sack method of packing, useful if you're planning on taking your Tux and Black Tie outfit https://kriega.com/adventure/ks40
Unfortunately, they sent me two of the smaller bags that are 9" wide by mistake, rather than one 9" and one 10.5"!! That being said, the 9" bag is actually too wide for the smaller pannier, which is only 7.5" wide.