In this case Art I would only be carrying a few extras in the sizes I know I might need. If the bits in the tool itself weren't such a good variety, I'd replace the integral ones with some of these...regrettably they're not double sided like the Victorinox ones are.

The original SAK bits have never fallen out once in nearly a decade of using it (crud...I'm using that word more and more...I must be getting old). That said, I have dropped them before and they're black...I'm surprised I haven't permanently lost one due to my butter fingers. Keeping these extras from falling out is going to make me get creative as it won't magnetize enough to hold the bits in...not with any of the magnets I have anyhow.