As I have already said, the photographic backpack will contain everything you should never lose on your way. It sounds little bit foolish, but in small backpack goes twice more stuff as it is expected to. Take a look on small photo backpack of 25x20x30 centimeters size and try to put in all of necessary equipment.
Beside of camera body, you will need additional lens, filters, fast battery charger and adapters, few packs of batteries, cables, memory cards, dust blower, cleaning brush, portable disk or burner and other stuff. I suggest you to squeeze into also your medicines, documents and maps. On rucksack side can be buckled one vest or wind stopper, and tripod on the other side. Pocket knife, pincer and similar tools can be in your pockets, but I can assure, you have enough of place in your rucksack. You wont lose them too easy. Put the needle in a small plastic tube. Don't forget indispensable cables and adapters, your disk and batteries are dead without them.
I use thin transparent sling for fasten the rucksack to my belt. I can then freely put the rucksack down and left it near me. If someone try to steal it, will be surprised because the rucksack will be ready to go with him only for a meter. I used it only in Buenos Aires, the travel over the country seemed safe to me.
Believe or not, all of this stuff goes into this small rucksack you are seeing on the picture. Moreover, I carried in it also my electric razor, protection cream and anti-mosquito spray. I didn't put in only my additional camera although I could. That one is of less value so I put it into my luggage.