One of the examples given here is "Mon stylo s'est cassé alors j'en ai acheté un autre".
It seems to me that "Mon stylo s'est cassé alors j'ai acheté un autre" would work just as well, because "un autre" implies "un stylo". So would the second version (i.e. without "en") be: a) OK; b) clumsy; or c) just plain wrong?
Thanks