Yes a 13 year old can wear diapers for bed wetting.
You can buy youth sized disposable diapers online or even Goodnites brand bed wetting pull ups for your 13 year old or other branded pull ups in stores such as Walmart, Dollar General and much more.
They make all sorts of bed wetting diapers for youth who wet the bed.
However don't force your 13 year old to wear diapers for bed wetting but let them decide if they want to wear the diapers for bed wetting.