How do I keep clothes on my 20 month old?

This is my third child and my first to decide he is completely allergic to clothing. We can't get him to keep his clothes on most of the time and right now it's still too cold where we live for him to run around in next to nothing. I have been using the safe diaper pins to pin the zippers closed on his sleepers, but I don't have enough of them for him to wear them all the time and even with the overnight diapers he usually has leaked on them by morning, so just doing that all the time isn't an option.

Has anyone with a similar child found a good solution? Once summer hits I'll probably just live with the problem unless he keeps taking his own diapers off. He's sneaky about the diapers and waits until I'm in the bathroom or equally distracted and cleaning the diaper contents up is getting really old!

He's a sweet little guy and frankly puts his older sibs to shame in most areas, with the exception of this little stunt he has been my easiest child by far. My older two both tried this about once each and never did it again after a mild scolding, but no age-appropriate consequence has swayed this determined little stinker.

Help me out! I'm getting sick of continually scrubbing the kid, the carpet, the house, etc. when he decides to go au naturel.