Marinoni!!! I swear I'm starting to sound like a broken record.
It isn't so much custom as it is the ability to alter the geometry, paint, and frame options of any of their frames. (How that differs from "custom" i'm not sure). Anyway, "custom options" can be had for about $100 cdn above the cost of the frame.
A ciclo (their sport tour model made with columbus zona) starts at $600 cdn. That's a custom frame for around $550 American dollars!!! I'm buying one myself very soon. This isn't a fly by night company guiseppi marinoni has been building world class frames for over 30 years. Maybe i should copy and paste this response into a file somewhere so I can dig it out again next time someone asks for an "affordable custom frame"