When you say travelling, do you mean for walking, sitting in a plane/train, having on the go, or a combination of all of them?
I've got a couple alternatives -- the senn mx500 earbuds are my ultra-portables... they fit anywhere and go with me everywhere. pop 'em in, pop 'em out, and there ya go. very little isolation, however.
The ksc-35 and ksc-50 are also options that are ultra portable and would fit in my pocket. they are a little less convenient in that they are harder to just pop on and off, and i'm also more self-concious when i have them on. for this reason, they usually are relegated to my bedside, but they would make great portables (but offer little to no isolation).
I've been considering picking up a pair of Sony EX70 for that convenient earbud-style but with a degree of isolation. Opinions vary on sound likeability, but if you are at all curious I'd encourage at least a test-listen. If you don't want them I'll take them off your hands
The koss portapros are my second in travel command, and they give me a little extra when i need it over my mx500's. they are slightly less portable, due to size. but i like wearing them around my neck. again, these offer very little isolation.
If I'm on an airplane or someplace noisy like that, I used to bring my HD280 because they block everything out (and I'd be sitting down rather inconspicously). The Senn HD280 or Sony MDR-V6 both isolate very well, and they both fold up so they'll fit in a travel bag or backpack. These are next in my portable chain -- for when I want that extra bit of fidelity or isolation, but the bulk is difficult to deal with on a daily basis.
Finally there is the W1000, which never really leaves my room.