I used to keep extras in my car, but I live in San Diego, and found that my flanges and seals were melting into globby messes. I try to keep some in my purse, but then I need a bigger purse, it gets heavy, no good solution. Thankfully I don't have the accidents that I used to.
For you guys at work, what about a backpack (for your lunch and magazines, lol) or you white collar types could use a briefcase.