my son stopped napping at this age, and the only thing i could do was take him for a stroller ride or short car ride and he would sleep for an hour or so after - but sometimes it isnt worth it.
if he sleeps at night he may be getting enough sleep - mine has just started sleeping through (not every night but most) at FIVE!!
i used to have to hold mine down to take naps also, but i decided it was not worth it so i stopped them altogether, some babies need less sleep.
maybe instead of a nap he could go in a baby swing, or in the playpen for an hour instead, as long as you have a little break it doesnt matter if they are asleep.
we have the baby channel on direct tv, which is great for distracting babies for an hour or so, its only 5$ a month