Straight forks

You could do worse than the Volume Fu Manchu forks, they're dead straight, designed as trick forks for fixed gear bikes. Rake is 32mm. I think they're the ones that come on a built volume cutter. I'm riding these on my charge plug. I tried the charge nozzle, but the steerer tube was too short, but the Fu Manchu's is much longer. They're also a lot lighter than the nozzles, weighing in at around 900g. I bought them from here for £129: http://www.customriders.co.uk/prodshow.asp?prodid=11958&cat=0&parent=0&sid=3

bear in mind they're not drilled and have no mounts for brakes, so you'd need to be rudng brakeless.

They look threadless and also have a rake as you have stated. Would need to know the maximum rake the OPs frame could handle while still allowing a bar spin I would think.