gusset jury forks and kona p2's both have that or near that a-c length (both are sold out here in USA!)...sad
I found a set of spec-ed big tange forks on ebay (canti's only) that are a bit harsh (hard to find a steerer tube over 260mm!)
Have finally come to the point where I bought a mosso alum. fork on ebay with 410 a-c AND a iveke carbon with 425 a-c. Both are definitely not as flexy-nice as my ritchey...but with some 2.35 rubber on the wheel, hardly makes a difference.
Bikeman in usa carries a LOT of rigid forks, but for the price and for discs, I look to the east....