if you bought it from a vape shop (local shop) if they're cool they may give you it for free...my local B&M give pretty much anything free in small quantities(not going there daily and asking for stuff, more like once every few weeks) so far i've gotten free
coils...wicks...screws...they even gave me a Free RTA right out the box...but my local vape shop is run by a younger crowd and the owner seems to like me so ... maybe thats why....
i doubt they'll charge you for ONE screw though...unless they're mean...