If you examine the pump bearing carefully ,it should have a generic part number on it.It is usually 4 digits followed by letters. You can then search for a similarly dimensioned bearing or even upgrade to a higher temperature rated bearing. According to this link you can get a 1/4" Timken replacement inexpensively:
http://www.audiworld.com/forums/a6-s6-c5-platform-discussion-7/writeup-2-7t-secondary-air-injection-sai-pump-rebuild-1727056/
If you remove the bearing and take it to your local bearing store, you may even be able to get a ceramic bearing replacement. You just need i.d.,o.d. and width.Then decide what type of seals 7 grease you want. The bearings come in various grades(ABEC is common) but for this low stress application ,the utility grade is probably adequate.
Please let us know what you find and what you do to repair the pump.
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