Just some notes for future people looking for the same thing:
I have found, as with other members on this forum, that the Premium II drive works perfectly over USB in the original Premium-U enclosure. The original Premium-U enclosure uses the Cypress (In-System) ISD300A1 chipset, which is the same as your PX-W4824TU enclosure.
I can also confirm that the Premium II works perfectly over USB in the Premium II/2U enclosure (released only in Japan). This enclosure uses the Genesys Logic GL811S chipset.
Other members on this forum have also reported success with the Premium II using the Prolific 2507 chipset and the Genesys Logic GLE811 chipset: http://club.myce.com/f61/best-external-enclosure-my-plextor-premium-ide-drive-241874/
The last thing worth remembering when looking for an enclosure is the power rating. The Premium II has a fairly high power rating, at least compared to most modern drives.
Best of luck and keep us posted for future members with this question!