http://fhoude34.free.fr/PortableHD_Main.htmUnfortunately this page doesn't have information on plain USB 2.0 OTG drives, but it does have a lot (and I mean a lot!) of good information (either listed on the page or contained in the reviews/discussions that are linked from this page) on a large number of portable storage devices.
And as a quick summary, Savit Micro's
Nexto CF and the
CompactDrive PD70X are the two fastest PSDs (getting around or greater than 10MB/s with the right CF cards; and to my knowledge they are not sold in North America so you'd have to have them shipped worldwide), there are a few that get around 5MB/s (with the
CompactDrive PD7X being a popular model as it's cheap (~$120 US vs about 150 to $180 for the other two - and these prices
do not include the internal hard drive!) - but do note the comments under the 'Reliability & Polemic' section in Frederic Houde's
review of it), and all the rest (at least those which do have the actual CF to PSD transfer rates listed) are below 3.3MB/s - with a number of them being limited to USB 1.x speeds (1.5MB/s).