Hi,
I was looking for that exactly and sadly found that Bosch will not have any parts for sale to the public, the only option is to buy a unit from them, the good thing is that even rebuilt units (from reputable places) are factory rebuilt, the problem here are the tolerances.
Saying that.... I'll have to buy the unit for ~$1000
Check this web site for all information:
http://members.rennlist.com/jimwms/CIS/CIShome.html
Word of advise: Prior to hooking your brand new/rebuilt fuel distributor make sure you have cleaned the fuel tank perfectly, otherwise will jam it and basically break it again. In fact that happened to me, the rust was too much for the filter and jammed the piston, that sucks!
Good Luck
-J