I’m using iOS 7. I have looked elsewhere and I’ve read that to do this I must go to setting -> general -> usage -> “battery percentage on”, but unfortunately, I don’t have that option.
Your question contains the answer. The setting for turning on the percentage indicator is under Settings > General > Usage > Battery Percentage Indicator.
This should show at all times when your phone is unlocked, though I've noticed as of iOS 7 due to the modified menu bar (the signal strength indicator is much wider) that the percentage is sometimes hidden when I check my phone from lockscreen.
I think this might explain your issue. When you've got Bluetooth, Wi-Fi, a carrier, portrait lock, an alarm and do not disturb mode enabled there's not a lot of room at the top of the screen for that percentage number.
try to reset ipod by Holding the home button + the lock button for about few seconds until the Apple logo appears, normally you should not lose data, in any case you can sync to iTunes.
some iPods may no longer show a toggle for displaying battery percentage in the menu bar.