The plug housings should be available from BMW but not straight forward to look them up.
+1 on the buyers guide, they are priceless! I used the Standard brand injector connectors when I built my injector tester back in the day and I stocked a huge amount of Standard/Blue Streak in my shop

Check out the Standard brand expansion tank.

__________________
1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)