This part is listed by BMW as BMW part number 16116753452 (16-11-6-753-452) and is described as Genuine BMW In-Tank Fuel Pump for E52 Z8 Roadster and Alpina V8 Roadster.
This is a Genuine BMW fuel pump with a two year warranty. Buying a Genuine part will usually be more expensive than an OEM or aftermarket brand but you are assured that it meets BMW's designs for fitment, performance, and longevity. It will also be the very latest design, incorporating any updates or revisions that an aftermarket brand typically will ignore.
BMW Fitments:
Z Series
E52 Z8 (00-03) > Z8 Roadster (2000-2003)