I'm actually not a competitive battler, soooo I'm not 100% sure what's in OU. :X
I have a shiny Azelf, Jolly nature, that I could EV 252 SA/252 SP/4 HP, but I'd be interested in Riolu for it, all things considering.
I also have Jolly/Adamant Trapinch Lv. 10 with all their EVs (252AT/252SP/4HP). They do have the Effort ribbon, they just need to be leveled up. They have egg moves of Quick Attack (priority move on Flygon sounds useful to me!) and Fury Cutter.
I'd offer Lucario but I know you already have a few Riolus
I also have a few legendaries. CMT if you're not interested in the above, because it's fairly easy to EV and/or hatch something up, too.