It seems that many people install a fork drain screw for fork service.  Where do you find an appropriately sized washer to seal the bolt...., fiber, copper or aluminum?.

http://www.mcmaster.com/#97725a100/=wfbxa8

Or buy locally 6 mm copper sealing washer....

I counter sunk the threaded hole and put an "O" ring on the screw, it never gave me any trouble. 

I counter sunk the threaded hole and put an "O" ring on the screw, it never gave me any trouble.

yep, that's what the old ones had on the pre 94