I tried for years to get a good flash drive for an emergency disk. One that contained all my utilities for fixing or rescuing drives and the information on them. But the drives were just to small at one and two gigs. Well now that the prices of flash drives have dropped so low, now I find it is much easier to just buy a 16gb flash drive and put the whole OsX operating system on it. Of course this is the trimmed down version. Just the basic operating system. You will find this in the Leopard disk that came with your mac. Use the custom option.
I also tried the 8gb, but it is so slow (everything action crawls) and you have to trim down the operating system to an extreme in order to fit it in. But it can be done. But I’m much happier with the 16gigs.
Using the Leopard disk I have, I booted up from this and then formatted my flash drive using GUID and Extended Journaled with a partition of one. Then after it reboots you can update on the computer software update app or like I did, download the combo version off of Apples site.
Then just add the utility apps you want on the flash drive. Repair permissions and you have your new emergency disk. If you did it right, you should have just over 7gigs space left and it's much snapper performance than the 8gig or smaller. JonL
Emergency OS X Boot Device