it is a bad idea to co-hab species with different care requirements. another consideration is that these lizards are cheap because they're often wild caught in the pet trade. this means the chances of introducing parasites to your crested are pretty high.
IF you had a very large enclosure and treated the lizard for parasites, it's possible. but it's also possible one of the two would develop territorial tendencies and they would fight.
since neither species alone takes up that much space, why not get one and house it separately? reptiles don't need "friends"; your crestie isn't lonely.