Nov 27 2006: I do not have ANY affiliation with the eBay seller Roxsen, but I purchased their tripod collar for my 70-200 f4 L IS USM (purchased on 11/9 for $77 shipping included and arrived 11/15 to the USA from Hong Kong) and it works flawlessly. The collar is very close in color to the L, maybe a tad brighter but hard to tell in most lighting. The construction is solid metal and the turn-lock has a nice "seal" when tightened fully, just like my Canon L collars. [NOTE: While the 70-200 f4 lenses do not "require" a collar for tripod use, I STRONGLY recommend it. For example, if you use a 20D/BG-E2/7-2f4, and if you mount this combination to your QR plate and ballhead, you will find out how frustrating it can be to compose with precision because the weight of the body/grip/lens will cause a "drooping" and "sagging". What this practically means is that you will actually need to focus HIGHER than your intended/desired point, then tighten the ballhead, then HOPE that the center focus point "sags" itself to your desired composition. It really is a frustrating procedure. But with the collar, you will find your composition and framing to be quick and consistent and sturdy, with NO SAG or DROOP. Where you tighten your ballhead is where your focus and framing will be. No "guessing" about how much lee-way to give for the "sag". Another "perk" of the collar is that it makes going from the horizontal to vertical orientation (and back again) quick and easy. So I HIGHLY RECOMMEND using a tripod collar with the 70-200 f4 lenses.]
Jan 13 2007 Uupdate: Here is another company selling the identical item but cheaper http://stores.ebay.com/big-is-camera
Nov 18 2007 Uupdate: Apparently Roxsen (and other eBay stores) are now selling this particular collar in white color for about $40 shipped. So the prices have dropped. If you get one, be sure to get this exact one, compare the pictures from the sellers and make note of the differences (ESPECIALLY the turning knob).
NOTE: This collar fits 6 Canon lenses that I know of: 200 f2.8, 70-200 f4, 70-200 f4 IS, 80-200 f2.8 ("Magic Drainpipe"), 300 f4 non-IS, 400 f5.6.