Thanks for the replies - Dr Doug, do I dare wait a month to have testing done until we're back in Michigan with my regular Vet? Last night (to preserve the freshly-washed bedding), I duct-taped a towel around Jimmy's tummy, and although he looked at me quizzically, he hopped in bed and went to sleep. And had a "dry night" (maybe if he's somewhat bugged about the waistband, he won't sleep so deeply as to have a leak?). I thought about protective pads, but he DOES choose to sleep on the floor if he gets too hot in the bed.
In spite of his high-energy mix, Jimmy's pretty laid back; so I'm hoping the waistbands will be the answer? I'll find out tonight ;-)