Hi there
usually frogs do not require a companion, but its your choice. By the looks of the options you have, i would wait a bit for your frog to grow, if you get one that is smaller, he will be eaten! if you get the larger one, your frog will be eaten. i would wait a while for your frog to get larger. If you do find one the same size, Great!

Good luck finding a buddy for your frog!