April 2003 and this is your first post? Lurker.
Just MHO, but I wouldn't trust a bayo lug on a FSB that was held on by screws. To me it seems like there is potential to knock the FSB loose. If a bayo was really that important to me, I'd get a new barrel with a pinned FSB.
Again, just my opinion. (Wait a minute, you didn't even ask for my opinion. Oh well, I'm too tired to delete what I typed.)
To answer your question, I've never seen a replacement FSB other than one that needs to be pinned in place (this requires drilling the holes through the FSB and barrel for the pins; do it wrong and you could screw up the barrel or have a canted FSB). You should be able to buy these from manufacturers, like Bushmaster & RRA. I ASSUME you can.
Hope this helps.
Welcome to the board!!