After a while, I ran out of shower caps. I even bought a fancier one at the dollar store which also sagged out from the elastic part. So, I decided to go with the free plastic bags that you get at the grocery store. These are ok, but the plastic is thin and tears easily. And, some of the bags have predefined holes at the bottom (huh?). I don’t know why some have these, but maybe the manufacturers put them there so air can escape when packing them.
One bag doesn’t have these problems: the Target stores bag. These are thicker than your typical grocery store bag and they don’t come with holes. Best of all they’re free. The thickness of the plastic makes these bags last a long time.