I received a reply from the eBay seller. He has made enquiries of his various suppliers, but has been informed that, at present, the MK4007GAL and MK8007GAL drives have been restricted to "designated customers" (hmm - I wonder who that could be? Apple perhaps?
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This seems to be consistent with the line reported elsewhere on other threads regarding these drives. Anyway, he's still waiting to hear from some suppliers, but suspects he'll get the same story. If/when I have any updates, I'll post them here.