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How to display uptime in i3status bar?

I would like to display uptime in common units (so not just in minutes if it is over an hour; also not just in seconds if it is over a minute; e.g., "1:02:30" for 1 hour, 2 minutes and 30 seconds would be my ideal time format) in my i3status bar. I have not even been able to find how to show uptime in the i3status bar in any units. I found this repo on GitHub that seemed to claim to do this but copying these configs gave me errors related to difficulty executing the status_command line in this repo's config. Namely the status_command line is:

status_command ~/.i3/i3status.sh ~/.i3/i3status.conf

guessing it only works with an older version of i3. Any ideas how to do this? If it helps here is my present ~/.i3status.conf file. If my distribution is somehow relevant it is Gentoo Linux.