Thanks Robert. I wasn't 100% sure the breather was the same one used on the Merkur XR4Ti. I've dealt with the guys at Midwest Merkur - great folks - so I'll fire them off an email and see what they have available.
Of course, seeing as the Merkurs were officially brought to the U.S. by Ford, wouldn't my local Ford dealer be able to get these breathers?
Thanks again. Cheers!