If you are registered, you get access to the members only section, can participate in the buy & sell second hand forum and last but not least you can reserve your preferred username before someone else takes it.
Id contact Ardennes-coticule directly since they're the actual running mine for all coticules. You can ask Maurice, the owner of Ardennes, what kind of coticule is best for your needs. He then can hand pick one for fast sharpening, slow finishing etc depending on what you want.
Other sites just grab a coticule in a size you select and send it.
i would recomend steve, i have delt with him, and his coticules are all select from ardanees, thats a very good price with a box and deliverd, He also sells slurry stone. grab one why you can, thats perfect size also