You can try faking incontinence to get your parents to put you back in diapers by wetting your pants in front of them.
It might take a month or two of constantly wetting your pants in front of them to put you back in diapers.
But be aware though that your parents might want to take you to the doctor first to have some tests done and those tests can be painful.
Other ways you might get some diapers is by faking bed wetting at night. You can either just actually pee in your bed when you wake up in the middle of the night or pour some water on the bed each night.
If your parents don't put you in diapers then you might suggest to them that you're willing to wear diapers at night to keep your bed dry.
But don't act too anxious about it though as they might find out you're faking bed wetting or faking incontinence.