We all tend to lose our lenscaps and then have to buy more. Next time you drop yours over the taffrail or leave it in a hotel room, consider getting one of the White Balance Lens Caps from Promaster.
It clips in just like others, but features a translucent white center section that allows your camera to take White Balance readings in the custom mode - and to get an accurate WB for unusual circumstances. Consult your camera manual - in the case of all my Fujifilm X cameras it is as easy as one click with this lens cap.
Saves a heap of time later when you are finishing your jpegs!