Traveling with camera gear can be difficult. The cameras and lenses are obviously breakable, and you should never check them. Airlines claim they aren’t liable if your equipment is stolen (I’d love to see how that holds up in court, but is more of a pain than I would want to deal with. So you HAVE TO keep it with you.
For a carry-on that will safely hold your gear, the Think Tank Airport Security is probably your best bet. It can hold all the gear most photographers have, a laptop, wires and maybe a few other things. It has a TSA lock on it and a wire so that you can latch your bag to something immovable. It won’t prevent all theft, but it will keep it from being an easy target.
This is also great for media rooms where you have to leave some gear behind and the security guard is possibly too busy texting to watch all the gear (and doesn’t know who owns what anyway.) Also, if you aren’t carrying your gear every day on your trip, you can secure it in your hotel room. Just tons of benefits.
While not necessarily strictly a travel need, a polarizing filter should be in everyone’s bag. You should get a circular polarizer, because a linear will keep your metering and AF from working in many situations. You should also avoid using one on a lens that is wider than 28mm, because you will have pretty extreme vignetting and the sky will be really uneven. Unless that is the look you want. This Tiffen filter is a really good value. It is a 77mm filter, but you can get an adapter to use it on lenses with a smaller filter ring.