I actually have, in my possession, a Canon-made center-pinch cap.
The EF-M lenses come with them. In fact, it was one of the neatest "small" things about the EOS M I bought this past weekend.
I did a video review and put it on YT... haven't posted it here yet though.--
flickr | 'Cause I've been waiting, all my life just waiting
For you to shine, shine your light on me