The ones I use are no longer available but just go online and google "cotton granny panties" and you will get plenty of hits like JC Penneys, Bali, etc. You want the ones that are all (or at least mostly) cotton and have a very long side seam (i.e. full cut briefs) with no fancy lace trim. There may be a tiny bit of "looped" trim on the edge of even the plainest of panties but honestly it's not noticeable at all. With all but the closest of inspection they just look like plain white underwear and will cover a diaper nicely without adding bulk or heat.