Griff, there are anti-diuretic medications that can be used to reduce the volume of urine. Here is a link to a description and a list of brand names:
https://www.drugs.com/drug-class/antidiuretic-h...

Of course, you should check with your father’s doctor before starting any new medication.

I have liner pads I put in at night inside of the pull up. They are unisex and fasten with elastic straps and a button. That catches the most of the urine, and the pull ups get what leaks out. Try restricting liquids in the evenings too.

When I wake up at night I wake my wife up and take her to the bathroom . This has been helpful even though I hate to wake her , she falls right back to sleep.

In the unit we would double up on the adult incontinence products. Sometimes worked. Sometimes didn't for our diabetic residents.