Nope, though these guys are thinking about it.
"Sega Dreamcast Component Cable
We currently have a very rough, yet working, prototype of a Sega Dreamcast component cable. This was actually the first prototype we ever made that was put into cable form. Depending on levels of interest and the success of our Genesis/SNES component cables, we may turn towards development of a production quality cable.
The main difference between this cable and our other component cables is that this one supports 480p in addition to 240p/480i (288p/576i for PAL).
Why make a Dreamcast component cable when the console already natively supports VGA? Several reasons:
Not all TVs have VGA inputs. Newer, budget HDTVs in particular, have trended towards dropping support for it.
Not all Dreamcast games and software support VGA mode. This requires you to either fiddle with the coding on the disc (IP.BIN bootloader), or drop to s-video or composite video.
Like all our other cables, the signals coming from the console are analyzed and then conditioned for the best possible output."
I believe this is exactly what he was reffering to.
I'd love a Dreamcast component cable. My TV has no VGA inputs and one of my favourite DC games (Airforce Delta) doesn't work in VGA.