What size is the screw that attaches the mirrors to the fairings? Couldn't find the size anywhere on the forums or wiki.
I bought universal turn signals from bike bandit but can't mount it onto the fairing unless it's through one of the fairing holes. Any suggestions?

BTW - After months of tweaking, I was finally able to get the bike to work. Woot woot.

Hey I flexed my Google-Fu and came up with no information about the size and pitch of those bolts.  If you need to buy new ones you could get them on partzilla

http://www.partzilla.com/parts/search/Suzuki/Motorcycle/2005/GS500F/HANDLEBAR%20%28MODEL%20K4-K5-K6%29/parts.html

Thanks but I think I figured the screw size. Bought some M8x1.25 16mm screws from home depot today but they were too big. Got a ruler and measured about 1/4inch (ruler didn't have a metric) which roughly equals 6mm. Depth I'm going to say 10mm.

Any ideas on how to mount my turn signals onto the fairing?

Hard to say without seeing pictures of the universal mirrors.  Any reason why you went with universal instead of Suzuki mirrors?  Do they look cool?

When I bought the bike, it had handle bar mirrors. Original mirrors on fairings were sold awhile ago. I bought some off amazon but they didn't come with screws 

You might be able to find a pair of Suzuki mirrors in the For Sale section of this website.  Not sure what the mirrors you bought look like, but maybe the stock ones will fit and look right.

Crap, I shouldve done that instead, but I already have the mirrors in hand. They're OEM mirrors but I got the pair for 50 bucks