Misplaced screw for mid line bracket during assembly

I must've been sloppy while repairing my keyboard and can't seem to find a Philips head screw for the top part of the mid line bracket. It looks like it needs a deep long screw that I don't have. The longest screw I've tried to use just falls in the hole and doesn't twist at all (is not secure). Any idea what the exact specification of a screw I'd need for this?

I'm going to go ahead and assemble it anyway without it until I can get the proper screw. Do you think it'll be secure? It's placed right next to the fan.