In case you're wondering, I've found a few sure-fire cures to toddler constipation that have nothing to do with diet, laxatives, or other common remedies.
Option 1 - leave him with a sitter after running out of all the "easy" cloth diapers. Be sure all the cloth wipes are hard to find or dirty.
Option 2 - Think to yourself "He's been doing pretty great with this potty training, I think I'll just put him in underwear today". Then make sure you put him in underwear with NO side snaps or easy access.
Option 3 - Get him all nice and clean, put cute clothes on him, and don't sweat putting on a diaper with good leg elastic.
Poop will happen. Guaranteed, or your money back.