My opinion: look for a new LED flashlight. It will have the proper circuit and design to take advantage of LED capabilities including high brightness, PWM dimming, power efficiency, and heat management. Adapting an incandescent flashlight will always be a compromise in one of those.
Edit: I have a similar flashlight and I bought a tiny usb-c rechargeable flashlight that is brighter for 1/5 of the size. And for battery life, you can recharge your keychain size light with any usb battery pack.