The adult diapers that are closest to resembling current and modern baby diapers are Bambino Magnifico diapers.
They have Velcro Landing strips and Velcro Tabs and have an all over print like most modern baby diapers have.
They are not cheap but they are worth the cost to feel like a real toddler or baby when wearing them.
https://bambinodiapers.com/products/magnifico
You can also buy some larger baby diapers that are mostly plain white which are Gentle Steps Size 7 diapers from Dollar General.
I wear the Gentle Steps Size 7 diapers once in awhile and although they don't fit perfect, the diapers do fit good enough for fun.
Gentle Steps Size 7 diapers from Dollar General are good absorbent diapers.
If you're a teenager or adult with a small waist size then Gentle Steps Size 7 diapers may easily fit you or at least closely fit you.
I have a 32 inch waist and with some modifications I can fit partially into the Gentle Steps Size 7 diapers.
I take the cloth outer covering off the Gentle Steps Size 7 diapers and then remove the landing strip and cut it in half and glue the a piece of the landing strip to each side of the Gentle Steps Size 7 diapers using a hot glue gun.
Then this allows the tabs to stretch enough to attach to the diaper and hold it in place.
I also run some packing tape around the diapers waistband to keep it in place.
I mostly wear adult sized diapers but those Gentle Steps Size 7 diapers are very squishy diapers and feel great and are good for when I just want to play in diapers.
Sleeping in just a diaper or just a diaper and shirt feels great.
I get my best sleep when wearing just a diaper and shirt or sometimes just a diaper.
I love going to bed wearing a wet diaper that I just peed in and even sometimes I sleep in a poop filled diaper.
As a baby and toddler I used to sleep in just my diaper and it makes me feel like a toddler and baby again to sleep in just my diaper.
A benefit of sleeping in a diaper is that if I need to pee during the middle of the night I can just wake up, pee in the diaper and go back to bed.
I hate wearing clothes when I don't need too and so wearing just the diaper to bed feels great.
Around the house I also love wearing just the diaper and sometimes a shirt.
I also like sitting around in a warm wet squishy diaper that's soaked to the max.
I will wear my diapers and wet them until they are soaked fully and will even wear a wet diaper when it's leaking.
I love to be outside wearing just a diaper and shirt and then pee in the diaper even when full and let it leak down my leg or leak out the leg gathers onto the ground.
I also love to go down my slide in a wet squishy diaper as it feels very good to do so or jump on my trampoline wearing just the wet diaper.
Bouncing around on the trampoline in just the wet diaper feels so good.
Also I have a spring rocking horse inside the house that I love to ride on and rock back and forth on it wearing just the diaper.
It feels very good to do that as well.
A dry diaper feels good but a wet diaper feels even better.
I once stayed in the same wet diaper for 2 days straight but that was not a good idea as I got a rash on my butt and on my penis as well.
I got a bad rash on my penis and it was bad enough that the skin was peeling and red for a week.
So I don't recommend staying in the same wet diaper for too long as although it's fun it's not a good feeling to have the rash.