Many, many, many, years ago I had a Sonata that actually came with two single DIN size units in the dash. One was a cassette player/radio and the other a cd player. Both had metal brackets that screwed flush into the sides of the components and folded over to be screwed into the dash from the front.
Hyundai sold two different fascia plates. One to accommodate that setup and (I'm sure for a different trim level) a different one with room for a single DIN unit and it had a little storage space below it. You may find something similar for yours.