I don't share your problem! However.....
When I was diving commercially and technical deep diving we used to use a product called Convene. They are an external catheter that rolls on like a condom with an easy release adhesive that can then be collected into off board collection. In our case for diving they were just connected to a valve on the leg of the suit and vented to the water.
There is no reason why you could not use one of these hooked up to a bottle. It would be discreet and leave no mess.
I would suggest you are brutally honest when choosing your size. Most men are small or medium!!!!