Now, of course your cam with come with caps. But as it happens with small things, such as pens or lighters, these things are highly susceptible to get lost. This is exactly the reason why we suggest you to buy cheap caps on your lenses. You don’t need to know much of anything besides your lens’s size and there you go. There are tons of stores which deal with the selling of underpriced caps. While you can definitely shop online too, it’s better and easier to go to a camera shop where you can easily get the cap, you can try it on and see if it stays fixed on your lenses. And if that’s the situation, then have at least 2 more caps, just to stay on the safe side.
Also, you should never try to save money on caps. Your lenses are just like your eyes. You need to do all the best for them not to get hurt, scratched or damaged in any ways as changing lenses basically equals to changing your whole camera and this has a way bigger cost then a cheap cap.