Licktons has the Forster superlink in an 11 speed model, but it cost $20 or half what I pay for a Chorus 11 chain.

I've sucessfully used the special KMC link made for the Campy 5.9mm chain and others have used the SRAM 10 powerloc sucessfully. Those two links are the narrowest across the inside of the outer plates. There's more side clearance than would be ideal, but it doesn't seem to be an issue.

I tried a superlink model 4, but it clicked every time it went over the cogs.