Quill seatpost don't grow on trees.

Only one manufacturer left that I know, and the guy on eBay that sells them gets like $140 for them.

If the bolt is holding the seatpost, and just needs some support, I'd consider filing the top/end of the seat tube flat so a stainless wormscrew bandclamp could be wrapped around the seatpost and rest against the top of the seat post. I believe that this would take much of the stress off the seatpost bolt, leaving only the job of keeping the seatpost from rotating to the seatpost bolt. You might be able to ride the bike sometime as a beater this way.

Personally, I would retire the frame (after test riding it, if I had never ridden a carbon Epic before, just to be able to say I did). I test rode a Felt F90 with a cracked head tube twice, just before I took the bike apart to salvage parts last weekend.