It's not My Thing, but I've come across some adult baby porn and can share what I remember seeing.
Pacifier on a ribbon. It's mostly in your mouth or you're in trouble with a real or imagined parental figure.
Looking at picture books from your local library, which won't question what you check out. New books every few weeks.
Juvenile clothing. As a female, you have a lot of options. Childish printed fabrics, cartoon characters, socks to match, sneakers or other kid-like footwear, plenty of ruffles. You want to cover or minimize your body's adult woman traits.
Children's music in the background at all times. I'm out of touch with what the toddlers listen to these days, but I know it's out there.
TV shows for little kids while you are age playing. Watch whatever is aimed at preschoolers. Sit on the floor.
Nap time, whether you want to nap or not. You have to go to bed, lie down, ideally holding your favorite stuffed animal.
Rectal temperatures, just to make sure you're not coming down with something. Lots of petroleum jelly. This is a good precursor to that enema you're going to get.
A bath, not a shower.
Juice boxes or bottles for all beverages.
A toddler plate with separated areas for three foods, some of it cut up to be finger foods for the baby. Cheese cubes, dry Cheerios, some grapes...
Eating regular food with baby utensils--a small fork and spoon.
Baby decor in the bedroom--sheets, a poster or print, stuffed animals, a mobile over the bed... Only if no one is likely to see it and be bothered by what it implies.