Have you tried things like dimming the lights, playing lullabys, Baby Einstein DVD, warm bath w/ one of the calming body washes, etc.? Are you sure he's tired? Can you just let him fall asleep in his bouncy seat when he starts to look sleepy? My daughter used to drift off when she was ready. But there were times when I wanted my son to fall asleep by a certain time, so I did this thing where I would sort of smack him on the forehead (lightly LOL) and then let my fingers run down his face. He loved it and would be out for the count after about two minutes of it.
3b (with 3c tendencies) on modified CG