Have a look at Yubico's Yubikey; it sounds like it might be what you're looking for.
It's default (i.e., designed) configuration is to be used as a one-time pad for two-factor authentication online, but it also has a "static password" mode which will output (the same) 64 pseudo-random characters when a little green capacitative circle is touched. Works as a USB keyboard so it's universal and works even offline. The random string static password can be changed any time.
A little over 30 $ and arrives in a regular 30 gram envelope (which I thought was too cool to be true) and in no time flat.
Honestly, all the tricks of keeping an encrypted file on a USB key are at once a massive hassle and mostly unecessary. All you need is a password with reasonable entropy that you can't easily guess or bruteforce. Enter Yubikey.
I'm developing some OTP online authentication applications with their API; it's pretty neat, actually. I can vouch for its physical sturdyness, too.
Clarification: I offered this as an alternative to online password storage, especially as it's API based and can be used online. Though, it could also act as a replacement for multiple passwords, if you were comfortable with that.