Hi, If it's anything like the MVP2, that Silver bit folds over the plastic button base.
(Can't tell from your blurry pics - pull back a bit to focuss if you don't have Macro foccusing)
It's easy enough to take the top off the MVP2 and gently crimp it back in place - assuming you haven't lost the metal disc that sits below it? (like I did). You might even be able to crimp it without taking the top off. Post some better pics matey.
Anyways here's a pic of the MVP2 button fix that may help - the metal disc was exactly the right size from a cheap tactile button i bought.