The Thomson setback models only have 16mm of setback, compared to 20mm or 25mm for most conventional seatposts ( I chose my Thomson for that reason - I wanted less setback than a conventional post but more than zero).
Posts with a bit more setback than most:
Look have a post with three different setback positions (it's all carbon, and I think only comes in conventional road length around 250mm)
Selcof make a post with 2 setback positions (20mm and 40mm if memory serves)
Time have a laidback ("aero") model with but 40mm setback - I believe this one is very hard to find but you might get lucky on ebay. It's bombproof but very heavy.
There's also the Titec "hellbent" with about 40mm or so setback - it's aimed at MTBs, but is a funky bent post configuration that might not work for you if you don't have a lot of post out of your seat tube.