You can try to use a Strategos, but unless he's got some fast moving boots, the elephants will move out of the range of his Banner before it will affect. Also Elephants like to spread out for some reason. And later, get limps and things which cause them to spread out.

I tried it for a while and it didn't work. Though if you put them with a bunch of fast moving units on the battlefield ( so they have a higher base morale and wont rout from one hit ) and can bring him up behind it should work.