go buy an EZ out and use that, they look like a phillips bit and you just slowly unscrew the bolt with them.
or find a non-metric sized wrench that is slightly bigger than the metric size to force in there and take it out.
is there loc-tite on it? i'm confused, you said you bought a woodcraft cover but then you said you want to replace it. did you just buy it? i guess it's not the point.
did you actually break the allen wrench or did you just strip the bolt? FYI torque is only 7 ft. lbs on those
you can call woodcraft and get another bolt for that at 978-297-2977 or just get one from a hardware store (i'd get an original one from WC). they're only 25 cents.