I was cleaning out the injectors on my 300tdi today and one of the small brass(?) washers/spacers pinged off and disappeared into the ether somewhere. Does anybody have a spare or know where I can get one? Haven't been able to find a part number and I don't want to fork out for a whole injector.

You should replace them anyway if you have injectors out, some people anneal and re use them but they are really cheap
ERR4621