For those who have a Big Leef tailcap and would like to have some spare parts, here are the part numbers.
I am not sure if this switch is the original one used in the Big Leef, and I have not used it yet, but I have ordered a few similar ones including one that is suggested by a member here many years ago but the size does not fit. This one is a forward clicky, 2A 14V switch. The size fits. I think it can handle a 30W bulb.