Thanks for the encouragement. Pottying is a total no-go at this time, as we have tried all the positive incentives but are unwilling to force him against his will. DS has pretty much hated being naked from birth, and while he will undress for bathtime, he's really really unwilling to be diaper-off for any length of time right now. I figure he'll sort it out in his own time... but in the meantime, we just need to find a way to stop the floodgates at night.
Going in and changing his diaper is definitely an idea - I have a four-month-old who is still waking in the night so I'm up already. I will give that a try.
So, all the diaper doublers I've seen listed online basically look like... sanitary napkins. The Diaper Doublers will be hard to find locally, so I will have to order them online... or is there any reason I shouldn't just stick a sanitary napkin across the top of his diaper in the front? (He's a stomach sleeper and the pee is always at the front of the wasteband, as the absorbent padding there has just been asked to do too much.)