I was kidding a bit. This is more general, not just the rubber bumpers. I think shipping in this case would be very non-expensive. I think there are this kind of small dilemmas there. In this case, if you are from Europe, if you have some order coming anyway from SLS - that would be the most economical way. Second is the one you mentioned, third MB, I think.
What I started being careful recently is that sometimes these small items (or bigger items) are cheaper in MB than in some of the internet stores or ebay. I always check that...