It's still in their catalog, part no 67-4589. Send an email to tomas@basmotor.a.se and ask if it's in stock. If you find it difficult to buy trough them, I may be of help (I want one myself) and reship it to you.
Don't know about the filter itself, but if original is not available I suppose it should be possible to make something up out of, for example, some round car filter element that would fit nicely inside the air box.
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