ipod touch dies quickly after full charge
My ipod dies and charges quickly
iPod, iOS 12
You can look into a batter replacement. I’ve had iPods since the 4th gen and they are very prone to the batteries losing their long life rather quickly (within a couple of years you will need to charge them several times a day)
If your iPhone or iPod touch won't charge - Apple Support
Another alternative is to have a charger at various places, or have a portable battery pack that you can use (i used to keep a charger at work)