How big does it need to be?

I suppose much depends on what the kit is intended for. You say for just one week, so I assume you are talking about a normal camping trip. Providing nothing goes wrong on this trip, then you COULD travel pretty light, but personally having experience of things going wrong, I prefer to carry a little more insurance.
My own survival kit is also my 18th century living history trekking kit. I learnt many years ago the advantages of pre 19th century gear & skills for long term wilderness living. When I go historical trekking, I go equipped for a long term stay, even though I may only be going for a weekend. I personally do not consider my pack to be overly large, it weighs 9 KG, but it is designed to last me a lifetime in the wilderness.
My knapsack is converted from my old haversack, so it is not large. But under the flap closure I secure a market wallet & my oilcloth shelter. My blanket roll is tied to the knapsack carry straps, & a spare pair of moccasins are tied to the blanket roll. These straps are wide & equipped with a chest strap.
Keith.



My belt pouch carries my fire bag with tinderbox, my fishing tackle & a brass sundial compass.
My powder horn is carried over the shoulder along with my shot pouch.


My fusil I carry in my hand or on my shoulder, tomahawk under my equipment belt at the back. Hunting knife & pistol under the belt at the front. Clasp knife in my waistcoat pocket & my legging knife in my legging on the right side.

If I had to leave my forest home in a major survival situation, then I would be carrying my sword as well. I do not expect to ever have to abandon my home in the woods, I am sure we can defend it, but in a survival situation I would probably be wearing my sword when ever I left the house along with my other tools of defence.

 

I use a old canvas alice pack with frame it carries 120 lbs easy be prepared carry as much as you can shelter fire water food are 4 must have comfy iteams are a bonus but do you need it ???

 

yes, Alice Pack here too, not easy to get in the UK but I managed to get one off Ebay cost me about £50, I wanted a framed pack and that's what came up.

 

I kept mine when they changed from canvas to nylon i had nylon one allso but my brother has it now i love my pack its 48 years old now and still good