Larry, I believe most cell phone batteries carry like warranties, I am pretty sure you can buy a Samsung Galaxy S4 replacement battery at Walmart that would do the trick.
Check the attached links, Good luck.
"I hope this helped you out, if so let me know by pressing the helpful button.
https://www.walmart.com/c/kp/samsung-galaxy-s4-replacement-batteries
https://www.amazon.ca/Samsung-Replacement-Battery-Discontinued-Manufacturer/dp/B00BW0X892
http://www.trustedreviews.com/news/samsung-galaxy-s4-battery-problems-samsung-offers-free-battery-replacements