Have you tried a standard crank puller, or am I missing something? Standard extractor threads are M22 - the self-extractor should be 22mm outside diameter. If the extractor threads are good then you’ll just need something to plug the hole for the puller to push against.
Edit: Never mind, just discovered that FSA use an M27 extractor thread. I read on on forum that this is the same size as a Cannondale Si/BB30 puller, but others say that’s M30. But I did find this: a bung for the end of the spindle