Does anyone know what all should be kept in a S.A.R dog pack?

Answer 1

SAR - meaning Search & Rescue? Anything you'd need in the field. Dog protection boots. Water. A packet of electrolytes would be good. collar w/ ID. Leash.
A few things on the mounted patrol I was on required - a compass (and knowing how to use it); a loud whistle; flashlights, whatever equipment the individual horse needed (protective boots etc). There is a list of things that were always kept ready in a "fanny pack" to be able to grab and go.
What conditions you'll be working matters too - if your dog is solid enough to be called to situations as varied as a bombing, wooded search, etc - you'd need to have equipment that you *might* need on such searches. Bad weather gear - comfortable boots and extra socks in a dry container.

Among the things useful:
Clothing:

•Hiking boots- Sturdy, lightweight.
•Socks- wool, polypropylene, or similar.
•Summer hiking pants.
•Wool or fleece pants.
•Insulated underwear tops and bottoms- Wool, polypro, acrylic.
•Glove liners- Wool, polypro, etc.
•Insulated gloves/mittens with shell.
•Gaiters
•Insulated jacket- Fleece, polarguard, down, etc.
•Vest or sweater- Wool, fleece, down, etc.
•Waterproof shell system- Parka and pants or bibs. GoreTex or similar waterproof/breathable fabric, or coated nylon.
•Assorted hats for various weather conditions.

Gear:

•Pack-Internal frame or frameless, approx. 2800 cubic inches or larger.
•Bivouac sack, space blanket, tarp or ultralight tent.
•*Sleeping bag- Minimum temp rating about 5-15o F.
•*Insulated sleeping pad- Thermarest or closed cell foam.
•*Backpacker's stove & fuel.
•*Cooking pot w/cover, utensils.
•Water bottles- Plastic widemouth, 1 qt or larger, depending on conditions. Enough for you and your dog.
•Food- Enough for 72 hrs. Compact, high carbohydrate, suggested items listed separately.
•Water purification- Pump filter and/or iodine tablets.
•Headlamp w/spare batteries & bulb.
•Compass
•Knife
•Sunglasses
•Sunscreen & lip balm
•Insect repellant
•Toilet paper
•Personal hygiene- Soap, toothbrush, toothpaste, comb, contact lens supplies, spare eyeglasses.
•Compact binoculars- a useful option.
•Notebook & pen or pencil- Waterproof paper is a nice feature.
•Flagging tape
•Safety orange vest for handler
•Firestarter kit
•Handheld radio- 5 watt, VHF-High band, w/spare battery. Should have multi-channel capacity, and be preprogrammed with common SAR frequencies or have hand programmable option.
•Signal mirror
•Signal flares and/or smoke
•Strobe light- You don't necessarily need all these signalling devices, but some why to signal long distance is useful.
•Ear plugs
•First aid kit- Human and dog, items listed separately.
•Leather/nylon lead
•Safety orange vest for dog
•Bells
•Cyalume light sticks
•*Dogfood- Enough for 72 hrs. under stress. Some dogs eat more, some eat less, so know your dog.
•Dish or squirt bottle to water your dog in the field.

*Items that may not always be needed in the search pack depending on remoteness of the search, but may well be needed at search base.

http://www.byteland.org/projectk9/k9pg2.htm#supplies

Answer 2

NASAR has a recomended ready pack list. Persoanlly I think it's a little overkill but you have to carry it if you want to be certified by them.

Link is below (.pdf file)