Ugh.
Tell us that's just a qualifying hole and the restriction is at the bottom.
It looks like it slotted and unscrews. yes?
Got two choices in that case. Buy the smaller ones or make out of set screws.
And we see the e-holes aren't threaded either.
If you have soft lead, you can gently plug the bottom or middle ones.
Or you can tap them and do the set screw thing.