FYI The part numbers you need are:

Front sprocket: 5VK-E7460-10 (15T)
Rear sprocket: 5VK-25445-01 (45T)
Chain: 9456X-08110 (520/110L)

Go to a Yamaha dealer and see what they can find that matches.

However, it's worth noting that the MT-03 was a US bike until a couple of years ago, so parts will be available for it from any Yamaha dealer. The front sprocket is the identical to the XT and the rear is the same but a 47T version.

As for the chain, any 520 pitch 110 link one will do and should be easy to get hold of in the US (although you might need an extra link if you use the a 47T rear).

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