I had a Duracell 300 flashlight lying around with the infamous defective power switch that drains the batteries down even when off. I designed a new switch assembly utilizing an on/off push-button toggle switch (no more variable brightness like the old one) and re-uses some of the parts from the old assembly.

Like the old switch assembly, the new assembly needs to be hammered into the end cap (press fit). The old one needs to be destructively removed from the end cap with a hammer to install this.

Link to the switch I used:
https://www.amazon.com/dp/B0BZJ51KLG?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1