ponyespressoSomeone on amzn say the snow peak lid for their 450ml mug will fit this soto 450ml. That particular lid is MGC053. Snow peak writes about that one "D 3.5" H 1" Fits in MG-053 or TW-122 (90*24mm )"
See below for measurements for the S P tw-122 and the soto mug from this drop.