http://www.sjscycles.co.uk/700c-1-1-...ack-prod15589/

There's that, but it doesn't have cantilever bosses, only rack ones.

http://www.spacycles.co.uk/

These guys do touring-specific parts, you could email them and ask about forks, you might find they can order something for you.

Also, the Carrera Subway has a fork with all the fittings you want, and it would probably be cheaper than the LHT one. Halfords might be persuaded to sell you one without the accompanying Carrera, and despite the reputation Halfords bikes have, it's a decent fork, made of 4130 cromoly steel.

Hope this helps.