Menstrual Underwear with no pantyline – KORA MIKINO. EU
CreativeArrowy Baby Diaper Changing Pad Waterproof Reusable Mattress Non- slip Breathable Cotton Gauze Menstruation Mat 11.8*17.7in - Walmart.com
Stephen King doesn't know what a pad is. You can't slip a mini in there when there's already a pad... There's a couple other examples of his knowledge of menstruation, including this
Underwear Slip for Menstruation and bladder weakness Taynie Deluxe XS - 11XL
Leak Protection Slips Pants. Discreet Period Panties Menstrual - Etsy
Safe Durable Silicone Menstrual Period Disc Non-slip Menstruation Alternative Cup No Side Effects For Night - Safety Short Pants - AliExpress