Don't meean to scare you, but, if you dont get the oil changed immediately most probably you will need to do the next change in less than 20,000 km (ie. the vibration will start sooner than 20,000 km)
Check with Stafford, they should have it. But, sometimes they do go out of stock. There is another place you could try (T**k Motors), but, agents are the best option (more reliable)