Alternate gnupg directory

At work, the keys in my ~/.gnupg directory are for work use (I'm not the only one who could potentially view this directory, i.e. root, admins, etc).  So I keep my own personal set of keys on a thumb drive.  I'd like to use these keys I store on a thumb drive, but gpg defaults to ~/.gnupg.  In order to use the thumb drive, I need to add the "--homedir /path/to/different/key/set" switch.  Is it possible to have FireGPG allow an alternative path to our .gnupg directory?

I tried manually setting gpg's path to "gpg --homedir /xxx/yyy/zzz" but it didn't work.

Thanks!

David