Here's my best guesstimate: the flag looks pretty small, maybe 9" max on each side. The lightest weight cotton cloth for handkerchief is around 3 oz/sq yd. (135 countries+50 states)/16 flags/sq.yd.*3oz/yd=34.7oz or roughly one kilogram. So not a lot, but not trivial in terms of space travel. Also much lighter than one lunar flag kit for the American flag that was planted, which weighed 4.3kg https://en.m.wikipedia.org/wiki/Lunar_Flag_Assembly