It's comforting to know that I am not the only person who has been thinking about this very issue.
I recently put the following BOB together. Although I have both full field gear (second line) as well as a LBE assembled for vehical patrols or patrols close to home, I knew I wouldn't want to load this gear into my car for regular business trips.
So I decided to build a kit based on what many security contractors in Iraq are using.
This BOB is small enough to easily toss in my car and hide under a coat in the backseat. It's fairly basic at this point but I wanted to keep it simple and then add other needed items as conditions demanded.
Here's a gear list:
$50.00 (50 x $1.00)
Cold Steel SRK knive and sheath
Multi-tool
Local Map
Blow out kit in a vacuum sealed bag (Guaze, H-Bandage, Gloves, Tournique, duct tape)
Tramadex (Blood clotting medium)
Israeli pressure bandage
Small container of pain killers and anti-inflamatories
120 rounds of 5.56mm ammo (4 x 30-round mags)
13-round G23 magazine
Extra batteries (2 x AA)
Flashlight w/batteries
Bic Lighter
Sharpie pen
3-Cliff Bars
5-drink mixes
2-liters of water (2 x 1-liter bottles)
Compass
This bag will suppliment the items that are always on my person:
Glock 23
Wallet (with ID, CCW's, Expense card, calling cards)
Chapstick
Cold Steel Recon folder
Cellphone with e-mail access
If conditions require I will place my AR-15 in the car as well.
I figure this is a good foundation that will allow me to get back to my home and resupply.
419!