i feel your pain...
FWIW, get yourself a set of German Stahlwille allen/hex sockets. they are manufactured to closer tolerances than even the hyper expensive Snap-On sockets. i know this won't help your current situation but from personal experience, Stahlwille hex head sockets cannot be beat.
old mechanic's trick; put a little valve lapping compound into the hex head then insert said socket. the lapping compound will help the socket grip and provide an even tighter fit.
as far as your current situation, others have pretty much covered your options but do check out Stahlwille's stuff...
http://www.toolsource.com/advanced_search_result.php?keywords=stahlwille&x=0&y=0