I believe that in most instances of a break down the very tool or part you need the most is laying right where you left it on your garage work bench. I have used such things as the metal clip from my garage door opener to barbed wire to resolve distress issues. At worse was pushing my A for a bit on down the road. 99 % of the times I have ever been broken down, someone, mostly strangers, stopped to help. This was both for my previous Model A's and my Russian Ural sidecar. That 1 % left was likely when I ended up pushing my old tudor down the road a bit. Carry what you wish to make yourself feel good and secure, but chances are Murphy's Law will remain intact and also the idea that any specifically needed tool or part will still be there on your workbench in your garage right where you left it.