hex.py is simple Python script that prints a hex dump of a file or standard input in a format similar to hexdump's "Canonical hex+ASCII display." The format is actually based on hexl-mode in emacs.
To install, download the most recent version of hex.py from the link(s) below, remove the version from the file name by renaming it "hex.py". (On Unix-like operating systems, it can make sense to rename the file to just "hex".) Place the file somewhere in your PATH and set execute permissions on the file if necessary.