T10 Screws Replacement on 21.5" 2011 iMac Hard Drive Bay

Hi,

I recently replaced my HDD (slightly prematurely, but understandably deceased) on my 21.5" 2011 iMac with an ssd. I lost one of the T10 screws that hold the drive to the upper part of the bay.

Right now I use a T8 screw to hold it in place. Will it hold? I call most computer shops and hardware stores in the area and they don't seem to carry any (It's basically in the middle of nowhere where I live - I had to order parts and stuff for the upgrade from a shop 50 miles away). I can order from eBay or Amazon but I would rather not since it's such a small order and I don't really need anything else.

Also, what is a good replacement? The store nearest to me have philips screws (not sure what size)

Any suggestion will be greatly appreciated

Reed