Wait for the seller to respond?
He doesn't seem to big on communication, but then neither were you when you let the payment for the original purchase slide.
the seller has listed the same (or similar item) again in a separate listing
So it is possible that he had multiples of the item?
and there was a shipping notification as well.
At this point, you bought, you paid (after some nudging) and there is a very good chance the seller shipped.
Not every seller uses tracking, especially on inexpensive items.
But very few sellers would PAY postage for an item they have no intention of shipping, especially since the buyer has a comeback on goods that are not delivered.
Wait until Day 20 after payment. If the item has not arrived, open an Item Not Received Dispute.