serpentine tensioner bolt

[jooooooe]

got another problem holding up progress, the bolt that holds the tensioner on the engine bracket (engine from a '92 RS).....well,..I lost it and finding one has been a nightmare. it's not just a regular bolt either it sets into a counter sunk hole, so either it has to have a allen head or a real small sockets size, anybody have one? or know where I might find the #*! thing, I've comb several u-pull it yards with no luck and....and...don't just stand there, HELP!!!!!