Riolu female with hidden ability is EXTREMELY EASY to get on GTS, so don't worry about this promotion.
Pokemon from Dream radar are offered on GTS for any common pokemon, You just have to look with this rules.
-Always look for female pokemon (for obvious reasons)
-Level is always a Multiple of five (5, 10, 15 ~up to 60), because the level changes as you complete the game.
-Use the location as Japan.
I'm looking right now on GTS, there is a Riolu female Lv.10 and tha trader is asking for a numel Level 10 female. Other one is asking for a beldum level 40 (that you can get on Giant Chasm).