Brock, sent you an e-mail. (about the Bi-pass) I'm not sure if they metal ones for the ST set up. Maybe for the ones they put in Mustangs. Could always paint the ones you have.
Check with local speed shops...they may know of a local welder that can make some from alluminum sheet metal...I see homemade ones sometimes on some of my racer freinds cars..
Your valve covers shouldn't be cracking in the first place...
My first guess would be one cracked for some reason, and when replaced, it was over torqued going back on. Second guess would be some kind of warping...