Unfortunately, none of them on ebay are the right ones. I need RC-988R
This is just one of the problems with modern electronics gear and creates huge consumer resistance and settling for a cheap sound bar.
Unfortunately I find that, that remote is not universal, and people have been unable to program universal remotes. It is worth a try though if you want to gamble. Worse apparently Onkyo will not supply replacement remotes which is a total disgrace.
So, until you find a solution, you will have to control it from the front panel.
I don't like Onkyo and they are not on my recommend list. This is just one more reason to advise avoidance of Onkyo.
That unit can't be more then three years old, so I would really get rough with Onkyo.