I wish my parents would've never potty trained me.
My parents never made me wear diapers all the time or at all past potty training.
Although when I was 8 years old I had to wear diapers the rest of the school year which was Pampers plastic backed diapers.
It was school policy then that if you wet your pants more than once per week then you had to wear diapers for the rest of the school year.
I had wished my parents made me wear diapers all the time at home.
It's unlikely your parents will make you wear diapers and I would just not tell them and buy the diapers yourself and wear them without them knowing.
You can get some cheap diapers from dollar general which are Gentle Steps Size 7 diapers for $5.00 per pack and they have 20 of them in a pack.
Gentle Steps Size 7 diapers are pretty big and I'm almost 33 years old and can almost fit into the Gentle Steps Size 7 diapers although they are not a perfect fit.
The Gentle Steps Size 7 diapers do fit by stretching the tabs out a bit and I use some packing tape to secure it around me.
Gentle Steps Size 7 diapers also are very absorbent and hold a lot of pee and are really great diapers that swell up nicely.
I love the SAP in the Gentle Steps Size 7 diapers from dollar general and they are a great diaper for the price.
I have a 32 inch waist so if your waist is smaller than 32 inches which mine was when I was 15 then the Gentle Steps size 7 diapers should easily fit you as a 15 year old.
They're cheap and worth a try and if you cannot fit perfectly into them then take the Velcro strip off and cut the Velcro strip in half and then glue one on each side of the diaper which is what I do.
Then they can fit and you can also add some packing tape to it if you want.
They only cost $5.00 per pack for 20 diapers which is cheap.