Anyone bolt their outer grill to the grill brackets?

[In The Ten Ring]

I had to drill out the rivets holding the outer grill to the grill brackets. The grill brackets were just too rusty and one was really trashed.

Now I probably could re-revit it back together but I'd rather bolt it. I asked this question before and was directed to buy these bolts but I am not sure how they'd ever tighten up, as the bolt head has no slot for a screwdriver.

I'd like to use a pan headed bolt with a slot, short, yet wide enough to take up the hole.

Anyway, what did others do? Pics would be nice. I would like to reassemble my grill this month.

Thanks!