Disc only forks are still sorta hard to come by as the industry hasn't fully grappled with the move to put disc brakes OEM on urban/road frames and forks as of yet but it's coming. C'dale factory forks are very hard to come by as well. I am presently in the process of installing a Mosso aluminum straight blade disc only fork on my '07 BB disc. Weight is 624gm. Cost with shipping from China was less than $65 and it seems to be a well made fork, for no more than city/parks/hard surface trails that I ride on it should be fine. You can find one of these on ebay.hk if you look. Mosso also makes a carbon fork that is about double the money, weighs a lot more, and is only dressed up with the carbon since the blades and steerer are still aluminum. Full carbon disc only forks can be had from Richey and Trigon and unless you are specifically weight conscious, I couldn't justify the cost vs. the weight savings over the aluminum fork.
There are other choices, cr-mo is easy to come by, very strong, usually in the 1100-1350 gm range, my BB disc was an ebay build, it came with a Dimension cr-mo disc only rigid fork which you can see pics of in the post your Bad Boy thread. Looks wise it doesn't really compliment the bike but it rides great. About $40 on auction.
Cannondale in an email explained the finsh on the BB as a DuPont jet black base, with a DuPont matte clear over that. So far the rattle can Krylon satin black that you can find at Ace hardware is the closest I can come to it and it looks quite nice considering it's a spray can. They also make a satin clear (part #1323) that I think would look almost dead on factory over black but it's near impossible to find on store shelves. Amazon and ebay have it for around $16/can after shipping. Ugh.. K-mart also sells it and can ship it. Krylon also makes a matte finish clear (part # 1311) but it's too dull. I tried it several ways and it just doesn't get any of that sheen at all.
I'll try and post a pic when I get this fork mounted. There are I am sure better made forks than the ones I mentioned, more expensive, exotic metals, I needed something that was lighter and like you, wanted something that at least looked like it "fit" the looks of the bike.
Another consideration would be the distance from the axle to the crown on the original fork. Simply installing a rigid fork is easy enough to do, but if it shortens the length the frame is designed around it could mess with the geometry of the whole bike. I have seen rigid disc forks that mention they are made to compensate for an 80mm shock or a 100mm shock. I'm no bike builder by any means but there are those on this forum that could shed some light on this part of your search for a replacement fork.
