Don't get a tank at all, they are a waste of money, if it has a screen top your snake will push it's way out (retics are a lot more active than burms), and your retic will outgrow it in a few months anyway.
Order a 6x2 or 8x2 PVC enclosure now from a quality vendor so you'll have it in a few months; retics typically handle extra space well and your male will grow into it soon enough. In the meantime you can set it up in the biggest clear plastic tub with a secure lid that you can get your hands on.