Broke my key fob - Now what?

Hatchy Zoom

2012 Mazda2
So my key fob battery was dead. So I replaced the battery. But I guess I pushed a little too hard on the little plastic tab to seperate the top and bottom part of the fob, and... I broke it. So what do I do now? Both parts work, but they won’t come together anymore. For now, I’ve just put the top part away and am using the bottom part along with the standalone key. How much is this little plastic tab going to cost me if I want to put it back together again?