I use KeePass and encourage it's use to anyone I help out who runs into password troubles.

In terms of portability, there are versions for almost every platform out there, including phones. So if you can't use a flash drive have it on your phone. Yes, it's definitely harder to transcribe it from your phone, but it's manageable.

If you are concerned about one file having all you passwords, then break it in to two files one for high security and one for low security. The other option is to just make this one of your handful of really secure passwords that you simply need to remember to get in to your "machines". Machine login(s) and then your password safe login.

I have two files one for work and one for home, both are relatively secure passwords. To mitigate the possibility of losing everything with one file, I have a self enforced process of syncing the password file from my computer to my flash drive every time I change my password. For work, this has bailed me out twice after changing my login password which IT requires relatively high complexity and way too frequent of changes. I didn't end up using it enough that day that I changed it and muscle memory was still on the previous password. I came in the next day and blanked. Fortunately it was easy enough to bring up KeePass on a different computer and check my password. That has helped cement my process to ensure I have it synced after a password change.