With this parts you can install a 26,5mm LED drop-in (originally for a UltraFire WF-501 / WF-502) in a MagLite D-Cell.

These are available in many variations:

• https://www.amazon.de/gp/product/B07L589495
• https://de.lightmalls.com/smo-26-5-mm-cree-xp-l-v5-1a-1800-lumen-3-18v-1-modus-led-d-m02647
• https://de.aliexpress.com/item/1005003667664380.html
• https://de.aliexpress.com/item/4000389106001
• https://www.ebay.de/itm/404592437958

Pay attention to the right voltage, also consider the heat output of the new LED.

Strongly recommend to use high temperature filament, like PETG or ABS.

I test printed in ABS, which was shrinking quite a bit, so you maybe need to size down the parts a bit.

The original bulb holder need to be shortened about 2mm, also bend the little metal tap outwards, so it will make contact with the spring of the new drop-in. Screw a 5-8mm M3 in the bulb-insert and insert it instead of the original bulb.

See photos for more details.