However, even if you always use a stove instead, lids invariably fall off the pots if they are packed without a stuff sack, spilling their contents all over the pack. So the stuff sack is needed regardless!

Before trying custom sewing, you might want to measure height and diameter of the pot and check dimensions of various silnylon (that's silicone-impregnated nylon) stuff sacks that you can find online. You very possibly will find a fit!