Intentional Urination in bed

Looking for advice for our 5 year old son diagnosed with ASD. He has been fully toilet trained for 18 months but for the past 8 weeks has been intentionally wetting in his bed, our bed or on his windowsill. We know it’s intentional because he is dry at school and whenever he is out of the house and he seems to enjoy laying or sitting in the urine (he is a sensory seeker). I don’t want to go back to nappies because that feels like a step back when he has been in pants for 18 months but I’m at a loss at what to do. To confirm, he doesn’t wet in his sleep, and he waits until he is alone to do it so we know that, whilst it is in response to a sensory need, he does still have bladder control. Thanks.