Ultrafire Z5 tail cap/switch

Hey Fellas, new to the forum and the cause. I have an Ultrafire Z5 that I need a new tail cap/switch for. Does anyone have info on where I can get one??

Thanks.

More Info needed. My Z5 Switch is a OMTEN . DIA=16mm Narrow side=12.9mm. H =5mm, 9mm, 13mm . Front Spring = 19mm long. CHK with DX, KD & ?