Most motherboards use the same size M.2 screws. You can find these sold in such online stores like amazon. 

I'm kind of surprised that the Gigabyte board didn't use a standard size m.2 screw. I have used a screw from an ASUS board on my EVGA board since I was moving the SSD over and it was easier than finding the screw bag.

Contacting EVGA was the right way to go. While Amazon does have universal standoff screws, etc. pretty much all of them are labeled as being compatible with Asus, MSI, and Gigabyte boards yet never mention EVGA. In entering a support ticket with EVGA, I was able to explain the issue, and even to request a call to verify that I was explaining the issue/need correctly, resulting in EVGA sending me a replacement set of M.2 standoff screws and securing screws (come as a set) for all 3 of the M.2 slots, since I needed 3x new standoff screws. They were supposed to be sent as part of the replacement board originally, so the screw sets are being sent to me free of charge, thankfully.
 
It's still REALLY weird that no products out there on the internet actually are labeled as being EVGA compatible for standoff screws for the M.2 drives. Probably just another case of Google messing with the search results to provide the results that will give them the greatest revenue rather than what we actually search.