Tamron 77mm Snap-On Lens Cap

Tamron's unique construction allows you to take off and put back on the lenscap with a lenshood in the shooting position, and they are tight enough that they rarely fall off by accident like so many other supposed bargains will certainly do.  Available in the typical sizes between 52mm and 82mm.  If you put the function of something like a lenscap above other concerns then just try one-you won't regret it!