On Tue, 02 Jul 2013 16:18:02 +0000, Safeman
wrote:

I need to source 90 of 9/16 UNC flush headed countersunk bolts/screws
overall length 2" and 10 of the same but overall length 2.5"

It doesn't matter what type of drive they have and preferrably threaded
the whole way, I could live with 1/2" unthreaded shank.
Any more than that I guess would be acceptable, just a lot of thread
cutting for me to do....

Anybody help, I have run out of ideas...

You didn't mention where you are or where you've looked (of course
sigh) so I'll just say...

"Check with local fastener houses. Around So Or, it's Sasco.
http://www.sascofasteners.com/ . If your local distributor doesn't
stock them, they can find them for you and it will cost you 1/3 to
1/10 of what it would cost at hardware stores. Barring that, googlit.
Good luck!"

--
A sound mind in a sound body is a short but full description
of a happy state in this world.
-- John Locke