Things I would want with me on a trip as you described:

First aid kit - a pretty extensive one in the suitcase and a basic one with me in the vest (with all the usual stuff).

Knife - I'd want a good fixed blade if possible. If not (for legal reasons), then I'd want a good size folder for self defense use (Spyderco Endura comes to mind). I'd also take a smaller folder for the everyday uses where you wouldn't want to pull out the bigger one. A SAK comes to mind for this one. I'd also have my multi-tool with me (mine's a Leatherman Wave). Yes...that's a lot, but I think they could all prove useful. I also believe in backups in case something happens to one. I'd never carry just one knife on a trip like this.

PSK - you've already got that covered.

Large Bandana or two. Several good uses for these.

Compass / Map. Just in case you get turned around. I'd want this to stay with me always...not just in the room.

Light - I'd want a good bright light with (at least) one extra set of batts with me. A small Streamlight Scorpion or Surefire E2 comes to mind. I'd also be sure to have a Photon or two thrown in. Use one as the zipper pull on your vest...it'll always be handy.

Water - as already mentioned, there are some containers that collapse as you use them to help save room. I'd also keep the aqua-tabs in the vest. This smaller "fall back" container would be used to supplement a larger canteen that I wouldn't be shy about carrying.

The space blanket is also a good idea. Little size and NO noticable weight.

A small dust mask might also prove handy in this part of the world. You could take a box and keep one or two in the vest folded up and utilizing very little room.

I also find a small pack of kleenex (the travel size) to be handy in far out places (blow your nose, TP, etc).

A small (travel size) bottle of hand sanitizer might be useful. I keep a .5 oz (15ml) bottle of Purell with me. Other than the obvious...it makes a great fire starter.

I'd also throw in an extra ink pen somewhere. The fisher space pen would be excellent.

Best of luck with your trip. <img src="images/graemlins/smile.gif" alt="" />