First, if I were you, since it sounds like you've been with Metro awhile, check with their people on Facebook. They are Very responsive there. Send them a message there and ask if you by chance have a Promotional Price Upgade in your account.
That basically allows a current Metro customer the same deals as a new activation customer.
Metro has some Great deals on phones now if you can talk them into that Upgrade.
The closest in size to your mini phone
, is probably the LG Aristo II, only $59 now for new activates and it's specs will annihilate your current phones. 6 months ago, Metro Gave my Mom an Aristo I that I played around with, it was a perfectly fine phone.
If I were you and wanted to stay with a Samsung, the deal there is the Galaxy J7 Prime for $149. It's a S7 Galaxy Jr for a Jr price, but it will be a good inch or so Larger than your current phone. If you wanted to dance on the dark side they have a deal for a $149 iPhonie 5S, a pretty good deal but on an aging phone. On the other hand, it's pretty close in size to your Core.
My very recent choice however, when the mics my Google Nexus 6 went TU, was the LG Stylo Plus for $149. Probably the best under $200 phone there is.
It is so good I am already drooling for a Stylo 4.
PS; If per chance, you go with the J7 Prime which I almost did too, I have the PERFECT case for it that I will make you Hella Deal on. $6 shipped to you. I accidentally ordered it for the J7 when I had a window open while researching them. Great case. My Stylo 3 Plus is in the same case for that model. Save you $2 on the Amazon price.
Good Luck,
Bruce in Ocala, Fl